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Navigation Rules Quiz

98 questions on the International Rules (72 COLREGS) and the U.S. Inland Rules. Every answer tells you which rule it comes from and why. Where the two regimes differ, the question says which one it means — that is where most mistakes are made. Nothing is scored anywhere but here.

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All 98 questions

The whole bank, grouped by part, with the answer and the reasoning behind it. Click a question to open it — handy for revision, searching the page, or printing.

General & Definitions

Rules 1–3 · 9 questions

Which set of rules applies to a boat operating on a lake inside the COLREGS Demarcation Line?
  1. The International Rules (COLREGS)
  2. The U.S. Inland Navigation Rules (33 CFR Part 83)  ← correct
  3. Neither — the Rules apply only at sea
  4. Whichever the operator prefers
Rule 1. Inside the Demarcation Lines the Inland Rules govern. The International Rules apply on the high seas and connected waters navigable by seagoing vessels.
A vessel complies with the letter of every Rule and still collides. Under Rule 2, is she exonerated?
  1. Yes — compliance with the Rules is a complete defense
  2. Yes, provided she sounded the danger signal
  3. No — Rule 2 also requires the ordinary practice of seamen and the precautions the circumstances demand  ← correct
  4. Only if the other vessel was the give-way vessel
Rule 2. Rule 2 is the "general prudential rule." Nothing in the Rules exonerates a vessel from the consequences of neglecting any precaution required by good seamanship or by the special circumstances of the case.
A sailboat has her sails up and her auxiliary engine running. What is she under the Rules?
  1. A sailing vessel
  2. A power-driven vessel  ← correct
  3. A vessel restricted in her ability to maneuver
  4. A vessel not under command
Rule 3. A sailing vessel is one under sail whose propelling machinery is NOT being used. With the engine engaged she is a power-driven vessel and loses her Rule 18 priority.
Your engine is off and you are drifting, not anchored or aground. Your status is:
  1. Underway, and making way
  2. Underway, but not making way  ← correct
  3. Not under command
  4. At anchor
Rule 3. Underway means not at anchor, not made fast to shore, and not aground. Making way means moving through the water under propulsion — drifting is underway but not making way.
A boat is trolling two lines astern. Under the Rules she is:
  1. A vessel engaged in fishing, with priority over power-driven vessels
  2. A vessel restricted in her ability to maneuver
  3. An ordinary power-driven vessel with no special privilege  ← correct
  4. A vessel constrained by her draft
Rule 3. "Engaged in fishing" requires gear that restricts maneuverability — nets, lines, or trawls. Trolling lines do not, so a trolling boat gets no priority at all.
A tug whose steering gear has failed and who cannot maneuver as required is:
  1. Restricted in her ability to maneuver (RAM)
  2. Not under command (NUC)  ← correct
  3. Constrained by her draft
  4. Still an ordinary power-driven vessel
Rule 3. NUC covers a vessel that through some exceptional circumstance is unable to maneuver as the Rules require. RAM covers a vessel whose WORK — dredging, towing, surveying — restricts her.
A vessel is "restricted in her ability to maneuver" because of:
  1. A mechanical breakdown
  2. The nature of her work  ← correct
  3. Her draft relative to the depth of water
  4. Heavy weather
Rule 3. RAM turns on the WORK: dredging, surveying, underwater operations, replenishment, launching or recovering aircraft, minesweeping, towing. A breakdown makes her not under command; draft makes her constrained by her draft (International only).
Rule 2(b) allows a departure from the Rules:
  1. Whenever the master judges it convenient
  2. When necessary to avoid immediate danger  ← correct
  3. Only with Coast Guard permission
  4. Never
Rule 2. Rule 2(b) permits due regard to all dangers of navigation and collision, and to any special circumstances, which may make a departure necessary to avoid immediate danger.
The term "vessel" includes:
  1. Only powered craft
  2. Every description of watercraft used or capable of being used as a means of transportation on water, including seaplanes and WIG craft  ← correct
  3. Only craft over 5 meters
  4. Only documented vessels
Rule 3. Rule 3(a) is deliberately broad — non-displacement craft, WIG craft, and seaplanes are all within it.

Steering & Sailing

Rules 4–19 · 25 questions

Rule 5 requires a proper look-out by:
  1. Radar alone, when fitted
  2. Sight alone in daylight
  3. Sight and hearing, and all other available means appropriate to the circumstances  ← correct
  4. The autopilot, when engaged
Rule 5. A proper look-out uses sight AND hearing AND every other appropriate means — including radar and AIS when fitted — to make a full appraisal of the situation and of the risk of collision.
Which of these is NOT a stated factor in determining safe speed?
  1. Traffic density
  2. The state of visibility
  3. The fuel remaining aboard  ← correct
  4. The vessel's stopping distance and turning ability
Rule 6. Rule 6 lists visibility, traffic density, maneuverability, background light, proximity of hazards, and draft against depth — plus radar factors. Fuel is not among them.
A vessel is approaching and her compass bearing is not appreciably changing. This means:
  1. She will pass safely astern
  2. Risk of collision shall be deemed to exist  ← correct
  3. She is overtaking you
  4. She is anchored
Rule 7. A steady bearing with decreasing range is the classic collision indicator. Rule 7 also says that if there is ANY doubt, risk shall be deemed to exist.
Action taken to avoid collision should be:
  1. A series of small course changes, so as not to alarm the other vessel
  2. Delayed until the last moment so the situation is fully clear
  3. Large enough to be readily apparent visually or by radar, and made in ample time  ← correct
  4. A course change only — never a speed change
Rule 8. Rule 8 requires positive action, made in ample time, large enough to be readily apparent to another vessel watching visually or by radar, and resulting in passing at a safe distance. A succession of small alterations is exactly what it warns against.
In a narrow channel or fairway, you keep:
  1. To the port side of the channel
  2. In the middle, where the water is deepest
  3. As near the outer limit of the channel on your starboard side as is safe and practicable  ← correct
  4. Wherever traffic allows
Rule 9. Rule 9 puts you on the starboard side of the channel — the maritime equivalent of driving on the right.
A 30-foot sailboat is sailing up a narrow channel as a loaded ship comes down it. Who keeps clear?
  1. The ship — power gives way to sail under Rule 18
  2. The sailboat — she must not impede a vessel that can navigate only within the channel  ← correct
  3. Neither; both alter to starboard
  4. The vessel that first sounds one short blast
Rule 9. Rule 18 expressly yields to Rule 9. A vessel under 20 m or under sail must not impede a vessel that can safely navigate only within a narrow channel.
Two sailing vessels approach with the wind on different sides. Which gives way?
  1. The vessel with the wind on her starboard side
  2. The vessel with the wind on her port side  ← correct
  3. The larger vessel
  4. The windward vessel
Rule 12. Wind on different sides: port-tack vessel gives way. Wind on the same side: the windward vessel gives way.
Two sailing vessels have the wind on the same side. Which keeps out of the way?
  1. The leeward vessel
  2. The windward vessel  ← correct
  3. The faster vessel
  4. The one on the starboard tack
Rule 12. Same side: windward keeps clear. The windward side is the side opposite to the side on which the mainsail is carried.
You are coming up on another vessel from more than 22.5° abaft her beam. You are:
  1. Crossing — she gives way if she is on your port side
  2. Overtaking — you must keep out of her way  ← correct
  3. Meeting head-on — both alter to starboard
  4. Under no obligation, being the faster vessel
Rule 13. More than 22.5° abaft the beam is the overtaking sector — at night you would see her stern light and neither sidelight. The overtaking vessel keeps clear until finally past and clear.
While overtaking, the bearing between you and the other vessel changes so she is now on your starboard bow. Now what?
  1. She becomes the give-way vessel under the crossing rule
  2. You are still the overtaking vessel and must keep clear  ← correct
  3. Both vessels sound the danger signal
  4. The situation becomes head-on
Rule 13. Rule 13 is explicit: no subsequent alteration of the bearing between the two vessels shall make the overtaking vessel a crossing vessel or relieve her of her duty.
Two power-driven vessels meet head-on. Each vessel shall:
  1. Alter course to port and pass starboard-to-starboard
  2. Alter course to starboard and pass port-to-port  ← correct
  3. Hold course; the smaller vessel gives way
  4. Stop and sound five short blasts
Rule 14. Rule 14: both alter to starboard so each passes on the port side of the other. When in doubt whether a head-on situation exists, assume it does.
You are a power-driven vessel. Another power-driven vessel is crossing from your starboard side. You:
  1. Stand on — you are the stand-on vessel
  2. Give way, and avoid crossing ahead of her  ← correct
  3. Sound two short blasts and alter to port
  4. Increase speed to cross ahead
Rule 15. The vessel that has the other on her own starboard side gives way. "If to starboard red appear, 'tis your duty to keep clear" — and Rule 15 adds: avoid crossing ahead.
The give-way vessel is required to take action that is:
  1. Early and substantial, to keep well clear  ← correct
  2. Minimal, to avoid confusing the stand-on vessel
  3. Only taken after sounding the danger signal
  4. Deferred until within half a mile
Rule 16. Rule 16 is one sentence: take early and substantial action to keep well clear.
You are the stand-on vessel and the give-way vessel is clearly not acting. You:
  1. Must hold course and speed regardless, until collision
  2. May take action by your maneuver alone to avoid collision  ← correct
  3. Must immediately alter to port
  4. Must anchor
Rule 17. Rule 17 permits the stand-on vessel to act once it is apparent the give-way vessel is not taking appropriate action, and REQUIRES her to act when collision cannot be avoided by the give-way vessel alone.
As stand-on vessel in a crossing situation, which maneuver is prohibited?
  1. Altering course to starboard
  2. Altering course to port for a vessel on your own port side  ← correct
  3. Slowing down
  4. Sounding five short blasts
Rule 17. Altering to port for a vessel on your own port side turns a near-miss into a collision — Rule 17 forbids it.
Which vessel has the highest priority under Rule 18?
  1. A vessel engaged in fishing
  2. A sailing vessel
  3. A vessel not under command  ← correct
  4. A vessel constrained by her draft
Rule 18. The order is: not under command → restricted in ability to maneuver → constrained by draft → fishing → sailing → power-driven.
A vessel engaged in fishing with nets meets a sailing vessel. Who keeps clear?
  1. The fishing vessel
  2. The sailing vessel  ← correct
  3. Whichever has the other to starboard
  4. Neither — they pass port to port
Rule 18. Fishing outranks sailing in the Rule 18 order, so the sailing vessel keeps out of the way of a vessel engaged in fishing.
In restricted visibility you hear a fog signal apparently forward of your beam. You must:
  1. Maintain course and speed and sound five short blasts
  2. Alter course to port and increase speed to clear the area
  3. Reduce to the minimum speed at which you can be kept on course, and navigate with extreme caution  ← correct
  4. Stop engines immediately in every case
Rule 19. Rule 19(e): reduce to bare steerageway, take all way off if necessary, and in any event navigate with extreme caution until the danger of collision is over.
In restricted visibility, which alteration should be avoided so far as possible?
  1. To starboard, for a vessel abaft the beam
  2. To port, for a vessel forward of the beam other than one being overtaken  ← correct
  3. Any alteration of speed
  4. Any alteration at all
Rule 19. Rule 19(d) says avoid an alteration to port for a vessel forward of the beam (unless overtaking her), and avoid altering toward a vessel abeam or abaft the beam.
Does Rule 19 have a stand-on vessel?
  1. Yes — the vessel with the other on her port side stands on
  2. Yes — the larger vessel stands on
  3. No — vessels not in sight of one another have no stand-on/give-way relationship  ← correct
  4. Only when both are power-driven
Rule 19. Rule 19 applies to vessels NOT in sight of one another. The stand-on/give-way rules of Section II require vessels to be in sight, so in fog both vessels must act.
Rule 8 says an alteration of course or speed to avoid collision should avoid:
  1. Any change large enough to be seen on radar
  2. A succession of small alterations of course or speed  ← correct
  3. Any reduction in speed
  4. Altering to starboard
Rule 8. Small successive alterations are hard for the other vessel to detect visually or by radar. Rule 8 requires action large enough to be readily apparent.
A vessel crossing a traffic lane must do so:
  1. At as small an angle to the traffic flow as practicable
  2. On a heading as nearly as practicable at right angles to the direction of traffic flow  ← correct
  3. Only at the termination of the lane
  4. Never — crossing is prohibited
Rule 10. Crossing is at right angles (Rule 10(c)); the small-angle requirement applies to JOINING or LEAVING a lane from either side (Rule 10(b)(iii)).
You detect a vessel by RADAR ALONE and a close-quarters situation is developing. Which alteration should you avoid?
  1. To starboard, for a vessel forward of the beam
  2. To port, for a vessel forward of the beam other than one being overtaken  ← correct
  3. Any alteration of course whatsoever
  4. Any reduction of speed
Rule 19. Rule 19(d): avoid altering to port for a vessel forward of the beam (other than one being overtaken), and avoid altering toward a vessel abeam or abaft the beam.
Which radar factor is expressly listed in Rule 6 as bearing on safe speed?
  1. The age of the radar set
  2. The effect of sea state, weather, and other sources of interference on radar detection  ← correct
  3. Whether the radar is Coast Guard approved
  4. The cost of the installation
Rule 6. Rule 6(b) lists radar characteristics, efficiency and limitations; scale in use; sea state, weather and interference; the possibility small vessels and ice go undetected; and the number, location and movement of vessels detected.
At night, you can tell you are the overtaking vessel because you see:
  1. Both sidelights and a masthead light
  2. Her sternlight only, and neither sidelight  ← correct
  3. Her red sidelight only
  4. Her green sidelight only
Rule 13. The stern light covers 135°, which is exactly the sector more than 22.5° abaft the beam. Seeing it alone puts you in the overtaking sector.

Lights & Shapes

Rules 20–31 · 25 questions

When must the lights required by the Rules be exhibited?
  1. Only between sunset and sunrise
  2. From sunset to sunrise, and in restricted visibility by day  ← correct
  3. Only when other vessels are in sight
  4. Only when underway
Rule 20. Rule 20: lights from sunset to sunrise, and also during restricted visibility in daylight. Shapes are exhibited between sunrise and sunset.
Over what arc does a masthead light shine?
  1. 112.5°
  2. 135°
  3. 225°  ← correct
  4. 360°
Rule 21. Masthead: 225° white, ahead to 22.5° abaft the beam each side. Sidelights: 112.5° each. Stern and towing: 135°. All-round: 360°.
Which light is yellow and covers the same arc as a stern light?
  1. The all-round light
  2. The towing light  ← correct
  3. The masthead light
  4. The flashing light
Rule 21. The towing light is yellow with the stern light's 135° arc, shown above the stern light by a vessel towing astern.
A vessel 20 m long must show a masthead light visible at what range?
  1. 2 nm
  2. 3 nm
  3. 5 nm  ← correct
  4. 6 nm
Rule 22. The 12 m–50 m band: masthead 5 nm; sidelights 2 nm; stern, towing, and all-round lights 2 nm.
At night you see a white light and a green light, no red. The other vessel is:
  1. Crossing right to left, and you give way
  2. Showing you her starboard side — she is crossing left to right  ← correct
  3. Head-on
  4. Overtaking you
Rule 23. A green sidelight is her starboard side, so she is moving left to right across your bow. You are on her port side, so under Rule 15 she gives way to you and you stand on.
You see only a white light dead ahead, no sidelights. The most likely situation is:
  1. A vessel head-on
  2. A vessel you are overtaking, showing her stern light  ← correct
  3. A vessel at anchor with a red light burnt out
  4. A vessel not under command
Rule 23. Neither sidelight visible with a white light showing puts you in her 135° stern arc — you are overtaking, and under Rule 13 you keep clear.
A towing vessel shows THREE masthead lights in a vertical line. This tells you:
  1. The tow is longer than 200 m  ← correct
  2. The tow is disabled
  3. She is pushing ahead
  4. She is restricted in her ability to maneuver
Rule 24. Two masthead lights in a vertical line for a tow of 200 m or less; three when the length of the tow exceeds 200 m.
A sailing vessel underway shows which lights?
  1. Masthead light, sidelights, and stern light
  2. Sidelights and a stern light — optionally red over green all-round at the masthead  ← correct
  3. Two all-round red lights in a vertical line
  4. Green over white all-round lights
Rule 25. No masthead light — that is what distinguishes her from a power-driven vessel. She may add red-over-green all-round lights at the masthead, but not with a combined sidelight lantern at the same place.
You see two all-round lights in a vertical line, green over white. That vessel is:
  1. Trawling  ← correct
  2. Fishing other than trawling
  3. A pilot vessel
  4. Not under command
Rule 26. Green over white: trawling ("green for a trawl net"). Red over white: fishing other than trawling. Note both fishing lights include a white light — pilot vessels are white over red.
Two all-round red lights in a vertical line mean:
  1. A vessel restricted in her ability to maneuver
  2. A vessel not under command  ← correct
  3. A vessel constrained by her draft
  4. A vessel aground
Rule 27. "Red over red — the captain is dead" is the traditional mnemonic for not under command. A vessel aground shows those two reds PLUS anchor lights.
Three all-round lights in a vertical line, red-white-red, identify:
  1. A vessel not under command
  2. A vessel restricted in her ability to maneuver  ← correct
  3. A vessel constrained by her draft
  4. A vessel engaged in fishing
Rule 27. RAM: red-white-red by night, ball-diamond-ball by day. "Restricted" includes dredging, surveying, underwater operations, replenishment, minesweeping, and towing.
Approaching a dredge, you see two all-round GREEN lights on her port side. You should:
  1. Pass to starboard of her — the green side is obstructed
  2. Pass on her port side — two greens mark the clear side  ← correct
  3. Stop and await instructions
  4. Sound five short blasts and hold your course
Rule 27. Two reds (or two balls) mark the obstructed side; two greens (or two diamonds) mark the side on which another vessel may pass.
A rigid replica of Code flag "A" displayed on a vessel means:
  1. Diving operations are in progress — keep well clear at slow speed  ← correct
  2. The vessel is anchored
  3. The vessel requires a pilot
  4. The vessel is aground
Rule 27. Flag "A" (rigid, at least 1 m high) plus RAM lights and shapes marks a vessel engaged in diving operations.
Two all-round lights at the masthead, white over red, indicate:
  1. A vessel engaged in fishing
  2. A pilot vessel on duty  ← correct
  3. A vessel not under command
  4. A vessel towing
Rule 29. "White over red — pilot ahead." Contrast red over white (fishing other than trawling) and green over white (trawling).
A vessel of 40 m at anchor must show:
  1. Two all-round red lights in a vertical line
  2. One all-round white light where it can best be seen  ← correct
  3. Masthead lights and sidelights
  4. Three balls in a vertical line
Rule 30. A vessel under 50 m may show a single all-round white light where best seen. At 50 m or more the forward light and a lower after light are both required. By day, a ball forward.
Three balls in a vertical line by day mean:
  1. Aground  ← correct
  2. At anchor
  3. Not under command
  4. Constrained by draft
Rule 30. Aground: three balls by day, or anchor lights plus two all-round reds at night.
A "flashing light" under the Rules flashes at what rate?
  1. 50 to 70 flashes per minute
  2. 120 or more flashes per minute  ← correct
  3. About one flash per second
  4. Any regular interval
Rule 21. A flashing light is 120 or more flashes per minute. Do not confuse it with the Inland special flashing light, which is 50 to 70 per minute and yellow.
An inconspicuous, partly submerged vessel or object being towed must show a white all-round light visible at:
  1. 1 mile
  2. 2 miles
  3. 3 miles  ← correct
  4. 6 miles
Rule 22. Rule 22 gives it 3 miles — the same as the all-round light of a vessel 50 m or more, and more than the 2 miles required of small craft, because it is hard to see.
A vessel engaged in minesweeping shows, in addition to her ordinary lights:
  1. Three all-round red lights in a vertical line
  2. Three all-round green lights, or three balls, arranged in a triangle  ← correct
  3. Red over green at the masthead
  4. A yellow flashing light
Rule 27. Rule 27(f): three all-round green lights or three balls — one at the foremast head and one at each end of the fore yard. Other vessels keep at least 1,000 m clear.
A sailing vessel is also being propelled by machinery. By day she must exhibit:
  1. A ball forward
  2. A conical shape, apex downward, forward where best seen  ← correct
  3. A diamond shape
  4. A cylinder
Rule 25. Rule 25(e). She is a power-driven vessel under the Rules, and the cone tells other vessels so. Under the Inland Rules a vessel under 12 m is not required to show it, though she may.
How far should you stay clear of a vessel engaged in mine clearance?
  1. 100 meters
  2. 500 meters
  3. 1,000 meters  ← correct
  4. 1 nautical mile
Rule 27. Rule 27(f): the three green lights or three balls indicate it is dangerous to approach within 1,000 meters of the mine clearance vessel.
A pushing vessel and the vessel being pushed are rigidly connected into a composite unit. They are lit as:
  1. Two separate vessels
  2. One power-driven vessel  ← correct
  3. A vessel restricted in her ability to maneuver
  4. A vessel towing astern
Rule 24. Rule 24(b): a composite unit is regarded as one power-driven vessel and shows that vessel's lights. Contrast an ordinary pushing arrangement, which is not rigidly connected.
A vessel engaged in fishing, other than trawling, with gear extending more than 150 m horizontally shows:
  1. A second pair of red-over-white lights
  2. An all-round white light, or a cone apex upward, in the direction of the gear  ← correct
  3. Three balls in a vertical line
  4. A yellow flashing light
Rule 26. Rule 26(c)(ii): the extra all-round white light or cone apex upward points toward the outlying gear so other vessels know which side to avoid.
A vessel of 50 meters or more at anchor must show:
  1. One all-round white light where best seen
  2. An all-round white light forward and a second, lower, at or near the stern  ← correct
  3. Two all-round red lights
  4. A single ball forward, at night as well as by day
Rule 30. Rule 30(a): forward light and a lower after light. The single-light concession is only for vessels under 50 m.
Under the International Rules, a power-driven vessel of less than 12 m may show:
  1. Nothing, if under oars
  2. An all-round white light and sidelights  ← correct
  3. Two masthead lights only
  4. A yellow towing light
Rule 23. Rule 23(d)(i). Separately, a power-driven vessel under 7 m whose maximum speed does not exceed 7 knots may show an all-round white light and, if practicable, sidelights.

Sound & Light Signals

Rules 32–36 · 14 questions

A prolonged blast lasts:
  1. About one second
  2. Two to three seconds
  3. Four to six seconds  ← correct
  4. Ten seconds
Rule 32. Short blast: about one second. Prolonged blast: four to six seconds.
Under the INTERNATIONAL Rules, a 15 m vessel must carry which sound-signaling equipment?
  1. Whistle, bell, and gong
  2. A whistle and a bell  ← correct
  3. Any efficient sound-signaling appliance
  4. None
Rule 33. International: 100 m or more — whistle, bell, and gong; 12 m to 100 m — whistle and bell; under 12 m — any efficient sound signal. Watch the trap: Inland requires the bell only at 20 m and above, so this same 15 m vessel needs only a whistle on inland waters.
You hear TWO short blasts from a power-driven vessel in sight. Under the International Rules she is telling you:
  1. I am altering my course to starboard
  2. I am altering my course to port  ← correct
  3. My engines are going astern
  4. I intend to overtake you on your port side
Rule 34. One short = altering to starboard. Two short = altering to port. Three short = engines going astern. Under the Inland Rules these are signals of intent requiring agreement.
Five or more short and rapid blasts means:
  1. I am backing down
  2. I am the stand-on vessel
  3. I do not understand your intentions, or I doubt you are taking sufficient action  ← correct
  4. I am anchored in a fairway
Rule 34. The danger or doubt signal. It may be supplemented by five or more short rapid flashes of an all-round white light.
Approaching a bend where other vessels may be obscured, you sound:
  1. One short blast
  2. One prolonged blast  ← correct
  3. Two prolonged blasts
  4. Five short blasts
Rule 34. One prolonged blast, answered by one prolonged blast from any approaching vessel within earshot on the other side of the bend.
In fog you hear ONE prolonged blast every two minutes. The vessel is:
  1. A power-driven vessel underway and making way  ← correct
  2. A power-driven vessel underway but stopped
  3. A sailing vessel
  4. A vessel at anchor
Rule 35. One prolonged = power-driven, making way. Two prolonged = power-driven, underway but stopped. One prolonged + two short = NUC, RAM, constrained by draft, sailing, fishing, or towing.
In fog you hear ONE prolonged followed by TWO short blasts. Which vessel is NOT a possibility?
  1. A sailing vessel
  2. A vessel engaged in fishing
  3. A power-driven vessel making way with nothing in tow  ← correct
  4. A vessel towing
Rule 35. That signal is shared by NUC, RAM, constrained by draft, sailing, fishing, and towing or pushing vessels. A plain power-driven vessel making way sounds one prolonged blast.
In fog you hear rapid bell ringing for about five seconds, repeated each minute. The vessel is:
  1. Aground
  2. At anchor  ← correct
  3. Towing
  4. Not under command
Rule 35. At anchor. A vessel AGROUND sounds the same bell signal with three distinct strokes immediately before and after it.
How often are the underway fog signals of Rule 35 sounded?
  1. At intervals of not more than 30 seconds
  2. At intervals of not more than 2 minutes  ← correct
  3. At intervals of not more than 5 minutes
  4. Only when another vessel is heard
Rule 35. Underway signals: not more than 2 minutes apart. Anchored and aground signals: not more than 1 minute apart.
Which is permitted as a signal to attract attention?
  1. A high-intensity strobe, which the Rule specifically recommends
  2. Directing a searchlight toward the danger, so as not to embarrass any vessel  ← correct
  3. Five short blasts, in all circumstances
  4. A red star rocket
Rule 36. Rule 36 expressly allows directing a searchlight in the direction of the danger. It requires that the signal not be mistakable for an authorized signal or for an aid to navigation, and says high-intensity intermittent or revolving lights such as strobes shall be avoided. A red star rocket is a distress signal and must not be used otherwise.
In fog you hear one prolonged followed by THREE short blasts. This is:
  1. A vessel not under command
  2. The last manned vessel of a tow  ← correct
  3. A vessel aground
  4. A pilot vessel
Rule 35. Rule 35: the manned vessel being towed (or the last vessel of the tow) sounds one prolonged plus three short, sounded immediately after the towing vessel's signal where practicable.
A pilot vessel on pilotage duty may add which identity signal in restricted visibility?
  1. One prolonged blast
  2. Two prolonged blasts
  3. Four short blasts  ← correct
  4. Five short blasts
Rule 35. Rule 35(k): four short blasts, in addition to the signal her underway or anchored status already requires.
A vessel at anchor may additionally sound which signal to warn an approaching vessel?
  1. Five short blasts
  2. One short, one prolonged, one short blast  ← correct
  3. Two prolonged blasts
  4. Three short blasts
Rule 35. Rule 35(g): a vessel at anchor may sound one short, one prolonged and one short, in that order, to warn of her position and the possibility of collision. It supplements the bell, it does not replace it.
On a vessel with whistles fitted more than 100 meters apart, maneuvering signals are sounded:
  1. On both whistles simultaneously
  2. On one whistle only  ← correct
  3. On the forward whistle in daylight and the after whistle at night
  4. On the bell instead
Rule 33. Rule 34(f): one whistle only, so the signal is not heard as two.

Distress & Exemptions

Rules 37–38 · 7 questions

Which of these is a recognized distress signal?
  1. A white flare
  2. Orange smoke  ← correct
  3. Two short blasts
  4. A green over white light
Rule 37. Orange smoke is on the Annex IV list, along with red star rockets, MAYDAY, EPIRB activation, continuous fog-horn sounding, flames on the vessel, dye marker, and the arm signal.
You have no flares, radio, or EPIRB. Which recognized distress signal can you still make?
  1. Sound one prolonged blast every two minutes
  2. Slowly and repeatedly raise and lower your outstretched arms  ← correct
  3. Show a green over white light
  4. Anchor and wait
Rule 37. The outstretched-arm signal is on the Annex IV list precisely because it needs no equipment.
On which VHF channel is a MAYDAY call made?
  1. Channel 9
  2. Channel 13
  3. Channel 16  ← correct
  4. Channel 22A
Rule 37. Channel 16 is the international distress, safety, and calling frequency.
Rule 38 exemptions can apply to vessels:
  1. Of any age, if the owner applies in writing
  2. Built or fitted before the Rules entered into force in 1977, where compliance is not readily practicable  ← correct
  3. Under 12 m in length, always
  4. Engaged in fishing
Rule 38. Exemptions are for pre-1977 vessels where compliance would require structural change that is not readily practicable. They carry time limits and must be logged and reported.
Which of these is NOT a recognized distress signal?
  1. A continuous sounding of any fog-signalling apparatus
  2. A white flare or white light shown to another vessel  ← correct
  3. A rocket parachute flare showing a red light
  4. Flames on the vessel, as from a burning tar barrel
Rule 37. White lights are used to attract attention (Rule 36), not to signal distress. Annex IV lists red flares and red star rockets — colour matters.
What is the signal consisting of a square flag with a ball above or below it?
  1. A vessel at anchor
  2. A distress signal  ← correct
  3. A pilot request
  4. A vessel aground
Rule 37. It is on the Annex IV list of distress signals, alongside the orange flag bearing a black square and circle, and the Code flags N over C.
A high-intensity white light used as a distress signal flashes at:
  1. 20 to 30 flashes per minute
  2. 50 to 70 flashes per minute  ← correct
  3. 120 or more flashes per minute
  4. Any rate
Rule 37. Annex IV includes a high-intensity white light flashing at 50 to 70 flashes per minute. Note that rate is also the Inland special flashing light rate — but that light is yellow and marks a tow.

Inland vs. International

33 CFR 83 · 18 questions

Which regime applies depends on:
  1. The size of your vessel
  2. Whether you are inside or outside the COLREGS Demarcation Lines  ← correct
  3. Whether you hold a license
  4. Whether the water is salt or fresh
Rule 1. The charted COLREGS Demarcation Lines are the sole dividing line. Shoreward of them the Inland Rules (33 CFR Part 83) govern; seaward, the International Rules.
Under the INLAND Rules, one short blast means:
  1. I am altering my course to starboard
  2. I intend to leave you on my port side  ← correct
  3. I intend to leave you on my starboard side
  4. I am operating astern propulsion
Rule 34. This is the single most-confused difference. Inland signals state an INTENTION about which side you will pass on; International signals state an ACTION you are taking. International one short = "I am altering my course to starboard."
Under the INLAND Rules, two short blasts mean:
  1. I am altering my course to port
  2. I intend to leave you on my starboard side  ← correct
  3. I intend to overtake you on your port side
  4. I doubt your intentions
Rule 34. Inland two short = "I intend to leave you on my starboard side." (Under International, two short = "I am altering my course to port." In the Inland OVERTAKING signal, two short means something different again: "I intend to overtake you on your port side.")
The Inland maneuvering signals of Rule 34(a) apply when vessels are:
  1. Anywhere within VHF range
  2. In sight of one another and meeting or crossing within half a mile  ← correct
  3. In restricted visibility
  4. Within one mile, in any condition of visibility
Rule 34. Inland Rule 34(a) is limited to power-driven vessels in sight of one another, meeting or crossing within half a mile. The International rule has no such distance limit.
You sound one short blast under the Inland Rules and the other vessel doubts the maneuver. She should:
  1. Sound the same signal back
  2. Sound the danger signal — five or more short rapid blasts  ← correct
  3. Sound one prolonged blast
  4. Say nothing and hold course
Rule 34. Inland signals require agreement. Agreement is the same signal echoed back; doubt is the danger signal, after which both vessels take precautionary action until a safe passing agreement is reached.
Under the INLAND Rules, how do you signal an intention to overtake on the other vessel's starboard side?
  1. Two prolonged followed by one short blast
  2. One short blast  ← correct
  3. Two short blasts
  4. One prolonged blast
Rule 34. Inland: one short = overtake on your starboard side, two short = on your port side. The two-prolonged-plus-short signals belong to the INTERNATIONAL Rules.
Which signal is required under the Inland Rules but has no International counterpart?
  1. Five short blasts for doubt
  2. One prolonged blast when leaving a dock or berth  ← correct
  3. One prolonged blast approaching a bend
  4. Two prolonged blasts in fog when stopped
Rule 34. Inland Rule 34(g) requires one prolonged blast on leaving a dock or berth. The bend signal and the doubt signal exist in both regimes.
Two vessels agree by VHF radiotelephone on how to pass, on inland waters. Whistle signals are then:
  1. Still mandatory in every case
  2. Not obliged, though they may still be sounded  ← correct
  3. Prohibited
  4. Required only at night
Rule 34. Inland Rule 34(h): a vessel that reaches agreement — for example under the Vessel Bridge-to-Bridge Radiotelephone Act — need not sound the signals. But if agreement is NOT reached, whistle signals shall be exchanged in a timely manner and shall prevail.
On the Western Rivers, a downbound vessel with a following current meets an upbound vessel. Who has the right of way?
  1. The upbound vessel, being better able to maneuver
  2. The downbound vessel, who also proposes the manner and place of passage  ← correct
  3. Neither; both keep to the starboard side of the channel
  4. Whichever vessel is larger
Rule 9. Inland Rule 9(a)(ii): the downbound vessel has the right of way, proposes the manner and place of passage, and initiates the maneuvering signals. The upbound vessel holds as necessary. This overrides both the keep-right rule and Rule 14.
On the Great Lakes or Western Rivers, a power-driven vessel crossing a river meets one descending it. Who keeps clear?
  1. The crossing vessel keeps out of the way of the vessel ascending or descending  ← correct
  2. The descending vessel, which has the current behind her
  3. Whichever has the other on her starboard side
  4. Neither; they pass port to port
Rule 15. Inland Rule 15(b) sets aside the ordinary crossing rule on these waters: the vessel crossing the river keeps out of the way of one ascending or descending it.
Which vessel category exists under the International Rules but NOT the Inland Rules?
  1. Vessel restricted in her ability to maneuver
  2. Vessel constrained by her draft  ← correct
  3. Vessel not under command
  4. Vessel engaged in fishing
Rule 18. Inland Rule 18(d) is [Reserved] and Inland Rule 28 is [Reserved]. The constrained-by-draft category, its definition, and its three all-round red lights are International only.
Under the INLAND Rules, at what length is a vessel first required to carry a bell?
  1. 12 meters
  2. 20 meters  ← correct
  3. 50 meters
  4. 100 meters
Rule 33. Inland: whistle from 12 m, bell from 20 m, gong from 100 m. International requires the bell from 12 m — a favourite exam trap.
A yellow light flashing 50 to 70 times a minute at the head of a tow is:
  1. A towing light
  2. A special flashing light, used on inland waters only  ← correct
  3. An all-round flashing light marking a hazard
  4. The signal for a vessel not under command
Rule 21. The special flashing light is Inland only: yellow, 50-70 flashes per minute, showing over an arc of not less than 180° nor more than 225°. Note a "flashing light" proper is 120 or more flashes per minute.
Under the Inland Rules, a vessel being pushed ahead (not a composite unit) shows:
  1. A sternlight only
  2. Sidelights and a special flashing light at the forward end  ← correct
  3. Two masthead lights in a vertical line
  4. Nothing; the pushing vessel carries all lights
Rule 24. Inland Rule 24: a vessel pushed ahead shows sidelights and a special flashing light at the forward end. A vessel towed alongside shows a sternlight plus sidelights and a special flashing light forward.
A 15 m vessel anchored in a Coast Guard special anchorage area on inland waters must show:
  1. An all-round white light forward
  2. Nothing — vessels under 20 m are exempt in a special anchorage area  ← correct
  3. Two all-round red lights
  4. Three balls in a vertical line
Rule 30. Inland Rule 30(g) exempts vessels under 20 m at anchor in a designated special anchorage area from anchor lights and shapes. Outside such an area the ordinary rule applies.
Which moored barge must display two all-round white lights under the Inland Rules?
  1. Any barge, at all times
  2. A barge projecting into a buoyed or restricted channel  ← correct
  3. Only barges carrying hazardous cargo
  4. Only barges over 100 m
Rule 30. Inland Rule 30(h): barges projecting into a buoyed or restricted channel; reducing navigable width below 80 m; moored more than two wide or over 25 m wide; or not moored parallel to the bank. Each shows two all-round white lights visible at least 1 nautical mile.
A 15 m vessel at anchor in fog on inland waters:
  1. Must ring the bell rapidly for 5 seconds every minute
  2. Need not ring the bell, but must make some other efficient sound signal at least every 2 minutes  ← correct
  3. Need make no signal at all
  4. Must sound one prolonged blast every 2 minutes
Rule 35. The bell duty attaches at 20 m under the Inland Rules. Below that, a vessel that does not ring must still make some other efficient sound signal at intervals of not more than 2 minutes.
Which sentence appears in International Rule 36 but not in the Inland version?
  1. You may direct a searchlight in the direction of the danger
  2. High-intensity intermittent or revolving lights, such as strobes, shall be avoided  ← correct
  3. The signal must not be mistaken for any authorized signal
  4. The signal must not embarrass any vessel
Rule 36. Both regimes allow the searchlight and forbid confusable signals. Only the International rule adds that the light must not be mistakable for an aid to navigation and that strobes shall be avoided.

Practice only — this is not a Coast Guard examination and passing it certifies nothing. Content is checked against the U.S. Coast Guard Navigation Rules and Regulations Handbook (corrected 12 August 2024), covering the 72 COLREGS as amended through IMO Resolution A.1085(28) and the Inland Rules at 33 CFR Part 83. The governing text is the handbook, not this page. Read it at the USCG Navigation Center.