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The real exam is passed module by module: Rules of the Road requires 90%, most other modules 70%. Chart-plotting modules are taken on paper and not included.
The free sample gives you 20 to 30 questions per module. The full bank contains every available official question, with written explanations on the popular small-vessel credentials, one-off $29, lifetime access on up to 3 devices, all credentials included.
The Master < 100 GRT (Near Coastal) credential is commonly called the 100-ton captain's license, or 100 GRT master.
You must pass each module separately. Rules of the Road requires 90%; most other modules require 70%. Chart-plotting modules are worked on paper.
The exam covers 4 modules: Rules of the Road, Deck General, Deck Safety, Navigation General.
This page includes free sample questions drawn from the official USCG sample examinations, with a full bank of around 331 questions across all modules available with lifetime access.
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A selection of free questions from the official USCG sample examinations. Use the interactive modules above for timed, scored drills.
INLAND ONLY Which term is NOT defined in the Inland Navigation Rules?
Why: Inland Rule 3 defines seaplane, restricted visibility, and underway, but deliberately omits 'vessel constrained by her draft.' That category exists only in International Rule 3(h) and has no status in inland waters.
INLAND ONLY Which of the following may be displayed by a law enforcement boat?
Why: The Inland Rules specifically authorize law enforcement vessels to display a flashing blue light when engaged in direct law enforcement operations. None of the other signals listed is authorized for that purpose.
INLAND ONLY Which of the following is indicated by a vessel displaying a flashing blue light?
Why: Under the Inland Rules a flashing blue light is reserved for law enforcement vessels engaged in direct law enforcement or public safety activity, so sighting one identifies a police or Coast Guard boat.
BOTH INTERNATIONAL & INLAND By definition which vessel is unable to keep out of the way of another vessel?
Why: Rule 3(g) defines a vessel restricted in her ability to maneuver as one whose work makes her 'unable to keep out of the way of another vessel.' The definitions of towing, fishing, and sailing vessels contain no such wording.
BOTH INTERNATIONAL & INLAND A vessel that is defined as "restricted in her ability to maneuver" is unable to keep out of the way of another vessel due to __________.
Why: Under Rule 3(g) the restriction must arise from the nature of her work, such as dredging, cable laying, or buoy servicing. Draft creates 'constrained by draft' (International only), and exceptional circumstances make a vessel 'not under command.'
INTERNATIONAL ONLY You intend to overtake a vessel in a narrow channel on its port side. The vessel to be overtaken has to take action to permit safe passing. How should you signal your intentions?
Why: International Rule 34(c): when the vessel ahead must take action to permit passing in a narrow channel, the overtaker sounds two prolonged followed by two short blasts, meaning 'I intend to overtake you on your port side' (Rule 9(e)).
INTERNATIONAL ONLY You are operating a vessel in a narrow channel. Your vessel must stay within the channel to be navigated safely. Another vessel is crossing your course from starboard to port, and you are in doubt as to his intentions. According to Rule 9, which statement is TRUE?
Why: When vessels in sight are approaching and you doubt the other's intentions or actions, Rule 34(d) provides the signal of at least five short and rapid blasts. Backing down or bound-to-hold signals are not prescribed.
BOTH INTERNATIONAL & INLAND In which situation do the Rules require both vessels to change course?
Why: Rule 14 requires each power-driven vessel meeting head-on to alter course to starboard, so both act. In crossing situations only the give-way vessel must initially act, and with wind on the same side only the windward sailing vessel keeps clear.
BOTH INTERNATIONAL & INLAND When two power-driven vessels are meeting head-on and there is a risk of collision, which action is required to be taken?
Why: Rule 14: in a head-on meeting with risk of collision, each vessel shall alter course to starboard so they pass port-to-port. Stopping, backing, or the doubt signal are not the prescribed actions.
BOTH INTERNATIONAL & INLAND Which is TRUE of a power-driven stand-on vessel?
Why: Rule 17 requires the stand-on vessel to hold course and speed, but permits her to act as soon as it is apparent the give-way vessel is not taking appropriate action, and requires action when collision becomes unavoidable otherwise.
Firefighting equipment requirements for a particular vessel may be found on which document?
Why: The Certificate of Inspection, issued by the Coast Guard, specifies the vessel's route, manning, and required lifesaving and firefighting equipment. Registry proves nationality; classification certificates address structural and machinery standards.
On the cargo manifest, which term is used to describe the weight of the cargo inside a box?
Why: Net weight is the cargo alone, tare weight is the empty box or packaging, and gross weight is both together. The weight of the contents inside the box is therefore the net weight.
Periodic surveys to renew the load line assignment must be made at which interval?
Why: Load line certificates are issued for five years, with renewal surveys at that interval; annual inspections in between verify nothing affecting the assignment has changed.
When oil is accidentally discharged into the water, what should you do after reporting the discharge?
Why: After notifying the Coast Guard, the regulations call for containing the spill and recovering the oil. Dispersants and sinking agents may not be used without authorization because they add to or hide the pollution.
The forecastle card is a copy of which document?
Why: The forecastle card is the copy of the shipping articles (the shipping agreement) posted where the crew can read it, showing the terms of the voyage they signed.
If you have to jump in the water when abandoning ship, your legs should be in which position?
Why: The proper jump position is legs straight down and crossed at the ankles, one arm holding the lifejacket down and the other covering nose and mouth. This protects the body on entry and keeps the jacket from riding up.
All personnel on board a vessel should be familiar with the rescue boat's __________.
Why: In an emergency anyone aboard may need to launch, board, or operate the rescue boat quickly, so all personnel must know its boarding and operating procedures, not its maintenance or technical details.
A situation has occurred where it becomes necessary for you to be towed. What action should be taken to prevent your vessel from yawing?
Why: Shifting weight aft sets the stern deeper, increasing drag aft so the towed vessel trails straight behind the towline like a weathervane instead of sheering from side to side.
Which action should you take after sending a false distress alert on VHF?
Why: A false distress alert transmitted by VHF voice is canceled by an all-stations voice broadcast on Channel 16, the distress and calling channel where the alert was heard, identifying your vessel and canceling the alert.
Charts should be corrected by using information published in which text?
Why: The Notice to Mariners (and Local Notice to Mariners) is published specifically for correcting charts and publications, listing chart-by-chart changes to aids, depths, and hazards. The other publications are themselves corrected from it.
Brief, violent showers frequently accompanied by thunder and lightning are usually associated with __________.
Why: A cold front forces warm, moist air upward rapidly, building cumulonimbus clouds that produce brief, violent showers with thunder and lightning. Warm fronts typically bring prolonged, steady precipitation instead.
Which level of accuracy can be obtained utilizing the U.S. Coast Guard's Maritime Differential GPS in an established coverage area?
Why: The Coast Guard's maritime Differential GPS broadcast corrections that provided 10-meter accuracy (typically better) throughout its established coverage areas.
Which indication on the barometer is most meaningful in forecasting weather?
Why: Weather is driven by pressure changes, so the trend, the direction and rate of the barometer's movement, is what forecasts. A rapidly falling glass warns of an approaching storm regardless of the actual reading.
Which kind of conditions would you observe as the eye of a storm passes over your vessel's position?
Why: In the eye, winds fall light and skies often clear while the barometer reads its lowest, but seas, no longer driven from one direction, arrive huge and confused from all directions. The eye is the pressure minimum, so high-pressure options are wrong.
Which agency publishes the Light Lists?
Why: The U.S. Coast Guard publishes the Light List, describing lights, buoys, and other aids to navigation in U.S. waters. Charts and tide data come from the National Ocean Service.
While on a course of 349°T, a light bears 13° on your starboard bow at a distance of 10.8 miles. What course should you steer to pass 2.5 miles abeam of the light, leaving it to starboard?
Why: On the present course the light is 13 degrees off the bow at 10.8 miles, so CPA = 10.8 x sin 13 = about 2.4-2.5 miles, with the light to starboard. Maintaining 349T already gives the desired passing distance.
If your propeller is racing in rough weather, which action should you take?
Why: Racing happens when pitching lifts the propeller near or out of the water, letting it overspeed and shock-load the shaft and engine. Reducing engine speed limits the overspeeding while keeping steerageway, unlike stopping entirely.
Which factor is most likely to impair the strength and durability of synthetic line?
Why: Ultraviolet radiation in sunlight breaks down synthetic fibers and weakens the line. Unlike natural fiber rope, synthetics are essentially immune to mildew and rot, so sunlight is their chief environmental enemy.
Which term(s) are in the category of "oil" as used in the Oil Pollution Regulations?
Why: The pollution regulations define 'oil' broadly: fuel oil, sludge, oil refuse, and oil mixed with wastes all fall within the term, so discharge of any of them is regulated.
What is the period of validity of a Merchant Mariner Credential?
Why: A Merchant Mariner Credential is issued for a five-year term and must be renewed before it expires.
According to the Lifesaving regulations in Subchapter W, fire and abandon ship drills must be held within 24 hours of leaving port if the percentage of the crew that has not participated in drills aboard that particular vessel in the prior month exceeds which percentage?
Why: Subchapter W requires fire and abandon-ship drills within 24 hours of leaving port whenever more than 25 percent of the crew did not participate in drills aboard that vessel during the previous month.
The water in which a vessel floats provides vertical upward support. Which term is regarded as the point through which this support is assumed to act?
Why: The buoyant force acts through the center of buoyancy, the geometric center of the underwater volume. The center of gravity is where weight acts downward, and the center of flotation is the center of the waterplane.
What is the SAFEST action to take with an accumulation of oily rags?
Why: Oily rags can self-heat and ignite spontaneously through oxidation. Discarding them as soon as possible removes the hazard entirely; storing them, even in a locker, leaves a spontaneous-combustion fire waiting to start.
If you wear extra clothing when entering the water after abandoning ship it will accomplish which of the following?
Why: Clothing traps a layer of water that the body warms, slowing heat loss and delaying hypothermia, the chief killer in cold-water survival. Buoyancy should come from the lifejacket, not the clothing.
Which statement is TRUE concerning the "flash point" of a substance?
Why: Flash point is the lowest temperature at which a liquid gives off vapor that will flash from an external ignition source. It is below the ignition (autoignition) temperature, where the substance ignites by itself, and below the fire point.
When a vessel's LCG is aft of her LCB, how will the vessel respond?
Why: The hull trims until the center of buoyancy lines up under the center of gravity. With LCG aft of LCB the stern settles, trimming the vessel by the stern, until LCB shifts aft beneath LCG.
The shoreline shown on nautical charts of areas affected by large tidal fluctuations is usually the line of mean __________.
Why: The charted shoreline in tidal areas is the mean high water line, the average of the high tides, so charted land may be surrounded by water at lower stages. Soundings, by contrast, use a low-water datum.
On a chart, the characteristic of the light on a lighthouse is shown as flashing white with a red sector. Which is TRUE of the red sector?
Why: Red sectors are arcs drawn to cover dangers such as shoals, rocks, or obstructions. Seeing the light turn from white to red means your bearing line lies within the charted danger area.
Your vessel is on a course of 221°T at 15 knots. At 0319 a light bears 198.5°T, and at 0353 the light bears 176°T. At what time and distance off will your vessel be when abeam of the light?
Why: Bow angles double from 22.5 to 45 degrees, so distance off at 0353 equals the run: 34 min at 15 kn = 8.5 mi. Beam distance = 8.5 x sin 45 = 6.0 mi; run to abeam = 6.0 mi = 24 min, giving 0417.
What is published by the U.S. Coast Guard?
Why: The Coast Guard publishes the Light List. Coast Pilots, nautical charts, and tide tables are products of NOAA's National Ocean Service.
You are steering 115°T, and a light is picked up dead ahead at a distance of 16.7 miles at 0522. You change course to pass the light 3.5 miles off abeam to port. If you are making 12 knots, what is your ETA at the position 3.5 miles off the light?
Why: Distance along the new track to the abeam point = sqrt(16.7^2 - 3.5^2) = about 16.3 mi. At 12 knots that takes 16.3 / 12 = 1 h 22 m, so 0522 + 1:22 = 0644.
Which term is given to a radar display which is oriented, so that north is always at the top of the screen?
Why: A stabilized display is gyro-referenced so north remains at the top no matter how the ship's head swings. On an unstabilized head-up display, the whole picture rotates with every yaw.
To find a magnetic compass course from a true course what must you apply?
Why: Going from true to magnetic requires applying variation, and from magnetic to compass requires deviation, so converting a true course to a compass course takes both (TVMDC, adding westerly errors).
The direction in which a vessel is steered is the course. The path actually followed is the __________.
Why: The course is the direction steered, but current and leeway push the vessel along a different path. The path actually followed over the seabed is the course over the ground.
Normally, your vessel is on a voyage of three months duration. How many sanitary inspections are required to be conducted during the voyage?
You are 15 feet off a pier and docking a vessel using only a bow breast line and stern breast line. Once the slack is out of both lines you begin to haul in on the bow breast line. What is the effect on the vessel?
Why: A breast line leads at right angles to the pier and moves only its own end of the vessel. Hauling on the bow breast pulls the bow alongside while the stern breast simply holds the stern at its existing distance.
When an Official logbook is not required, an unofficial logbook is required to be kept aboard for review by a marine inspector for __________.
Why: When no official logbook is required, the vessel must still keep an unofficial log of required entries aboard, available for review by a marine inspector, for twelve months.
When anchoring, good practice requires 5 to 7 fathoms of chain for each fathom of depth. Which is TRUE when anchoring in deep water?
Why: In deep water the long length of chain already out provides ample weight and catenary for a horizontal pull, so a smaller scope ratio holds well; using 5:1 to 7:1 in great depths would also exceed the cable carried.
Which action should be taken prior to assuming the Deck Watch while the vessel is in port?
Why: In port the moorings are the vessel's primary safety concern; tide, current, and cargo operations constantly change line tension. The relieving watch officer must verify moorings are adequate before accepting responsibility. There is no such thing as a blue mooring light.
Which is TRUE concerning the production of mechanical foam by a portable in-line foam proportioner?
Why: Because the proportioner is portable and can be inserted anywhere along the hose line, the nozzleman is not tied to a fixed foam station and can move freely. It does not change foam quality, bubble size, or production rate.
If the situation arose where it became necessary to tow a disabled vessel, which statement is TRUE concerning the towing line?
Why: A towline should have a catenary, a dip into the water. The sag acts as a spring, absorbing shock loads as the vessels surge, instead of letting the line come taut and snap.
What causes variation in a compass?
Why: Variation is the angle between true and magnetic north caused entirely by the Earth's magnetic field; it depends on location, not the vessel. Magnetism within the vessel causes deviation, a separate error.
Which defines a light's luminous range?
Why: Luminous range is the greatest distance a light can be seen based on its intensity and the existing visibility, ignoring observer height and Earth's curvature. Range limited by curvature and heights is geographic range.
Your vessel is leaving New York harbor in dense fog. As the vessel slowly proceeds toward sea, you sight a green can buoy on the starboard bow. Which action should you take?
Why: Outbound, the lateral system reverses: green can buoys you left to port entering are left to starboard leaving (red, right, returning). The buoy on the starboard bow is exactly where it should be, so hold course.
Aneroid barometers are usually calibrated to indicate atmospheric pressure in which units?
Why: Aneroid barometers carry dual scales in inches of mercury and millibars (hectopascals), the two standard units for reporting atmospheric pressure at sea.
When an azimuth of the Sun has been taken and the deviation of the standard magnetic compass computed, the watch officer should record the results __________.
Why: Computed deviations are recorded in the compass deviation log so a running record of deviation on various headings is maintained and trends or changes can be detected. The deviation card is only updated after adjustment.
A person who observes an individual fall overboard should do which of the following?
Why: The witness's job is to raise the alarm and never lose sight of the person, the hardest thing to regain. Leaving to fetch gear, or jumping in and creating a second casualty, both make rescue less likely.
You discover a leak in the fuel line to the engine. Which action should you take FIRST?
Why: Stopping the leak at its source comes first: close the tank valve to cut off fuel feeding the leak. Repairs, bilge pumping, or CO2 only matter after the flow is secured.
Which action should be taken once fueling has been completed?
Why: After fueling, gasoline vapors may have accumulated below. Opening hatches and ventilating all compartments (and running the blower) before starting the engine removes explosive vapors. Never start the engine first.
Which scale is considered a harbor chart?
Why: Harbor charts use large scales, larger than 1:50,000, to show harbors and anchorages in detail. Of the choices, 1:35,000 falls in that harbor-chart band; 1:150,000 and smaller are coastal or general charts.
Which is the BEST method of determining if a vessel is dragging anchor?
Why: Bearings of fixed shore objects change only if the ship actually moves over the ground, so a changing bearing is positive proof of dragging. Sheering and chain tension vary normally with wind and current at anchor.
Which is one of the limitations of foam as an extinguishing agent?
Why: Foam is mostly water, so it conducts electricity and must never be used on energized electrical fires; that conductivity is its key limitation. It floats on oil and can be made with salt water.
Aboard a vessel, what does dividing the sum of the longitudinal moments by the total weight yield?
Why: LCG is found exactly that way: sum of longitudinal moments (weight × distance from reference) divided by total weight gives the longitudinal position of the center of gravity.
Which term defines the strainer at the bottom of a bilge suction pipe to prevent clogging?
Why: The rose box (strum box) is the perforated strainer fitted at the foot of a bilge suction line; its holes admit water but keep debris from clogging the pipe and pump.
You are preparing to slush a stay on your vessel by lowering yourself down the stay in a bosun's chair. The proper way to do this is to ride down the stay on a riding shackle in which configuration?
Why: The shackle pin goes through the chair's bridle eye, where it is secured and cannot unscrew, leaving the smooth rounded bow of the shackle to ride and slide down the stay.
A vessel behaves as if all of its weight is acting downward through the center of gravity, and all its support is acting upward through which point?
Why: Buoyancy acts upward through the center of buoyancy, the geometric center of the underwater volume, just as gravity acts downward through G. The relationship of B and G determines stability.
Which is TRUE concerning fixed ballast, on small passenger vessels?
Why: Fixed ballast is part of the approved stability condition, so it may only be moved temporarily for examination or repair of the vessel, and only under a marine inspector's supervision.
When must a small passenger vessel of not more than 65 feet in length have a collision bulkhead?
Why: The regulations require a collision bulkhead in each listed case, exposed-water operation, more than 49 passengers, or over 40 feet on partially exposed waters, so all apply.
You are mooring to a buoy. How should you make your approach?
Why: Approach a mooring buoy heading directly into (stemming) the current. With the current dead ahead you keep steerageway at minimum speed over ground, giving maximum control as you ease up to the buoy.
BOTH INTERNATIONAL & INLAND When action to avoid a close-quarters situation is taken, a course change alone may be the most effective action provided that __________.
Why: Rule 8 says an alteration of course alone may be the most effective action if it is substantial (large enough to be readily apparent), made in good time, and does not create another close-quarters situation. Small successive changes are to be avoided.
BOTH INTERNATIONAL & INLAND You are approaching another vessel at night. You can see both red and green sidelights and, above the level of the sidelights, three white lights in a vertical line. Which vessel is required to have these lights?
Why: Under Rule 24, a towing vessel whose tow extends more than 200 meters astern shows three masthead lights in a vertical line, plus sidelights, which explains seeing red, green, and three white lights.
INLAND ONLY When two power-driven vessels are meeting on the Great Lakes, Western Rivers, or waters specified by the Secretary, where there is a current, which vessel shall sound the first passing signal?
Why: Inland Rule 14(d): on these waters the downbound vessel with a following current has the right-of-way, proposes the manner of passage, and sounds the first signal, because the current makes her harder to stop and maneuver.
BOTH INTERNATIONAL & INLAND When is your vessel traveling at a "safe speed" as defined in the COLREGS?
Why: Rule 6 defines safe speed as one allowing proper and effective action to avoid collision and stopping within a distance appropriate to conditions. It is not measured against other vessels, wake, or simply stopping within visibility range.
INLAND ONLY A law enforcement vessel patrolling a marine regatta may exhibit a flashing blue light or which of the following alternates?
Why: Under the Inland Rules, a vessel engaged in public safety activities, such as patrolling a regatta, may display an alternately flashing red and yellow identity light as the alternative to the law-enforcement flashing blue light.
BOTH INTERNATIONAL & INLAND Which is TRUE for a vessel using a traffic separation scheme?
Why: Rule 10 directs vessels to avoid anchoring within a traffic separation scheme or near its terminations, where converging traffic concentrates. Crossing, when obliged, must be at as near a right angle as practicable, not a small angle.
BOTH INTERNATIONAL & INLAND You are approaching another vessel on crossing courses. She is about one mile distant and is on your starboard bow. You believe she will cross ahead of you but she sounds a whistle signal of five short blasts. Which action should you take?
Why: Five short blasts is the danger/doubt signal (Rule 34(d)), she doubts you will keep clear. Rule 8 requires action that is substantial and made in ample time: a large, readily apparent course change, slowing if necessary.
BOTH INTERNATIONAL & INLAND Your power-driven vessel is stopped and making no way, but is not in any way disabled. Another vessel is approaching you on your starboard beam. Which statement is TRUE?
Why: A vessel stopped but not anchored or disabled is still a power-driven vessel underway. Under Rule 15, with the other vessel on your starboard side in a crossing situation, you are the give-way vessel; being stopped grants no privilege.
BOTH INTERNATIONAL & INLAND Which vessel should not impede the navigation of a power-driven vessel?
Why: Rule 18(e) requires a seaplane on the water to keep well clear of all vessels and avoid impeding their navigation. The other vessels listed are ones a power-driven vessel must keep out of the way of.
INLAND ONLY For the purpose of the Inland Navigation Rules, the term "Inland Waters" includes which of the following?
Why: The Inland Rules define inland waters as U.S. navigable waters shoreward of the demarcation lines, plus the Western Rivers (Mississippi River System). The Great Lakes are included only on the U.S. side, and waters seaward of the lines are COLREGS waters.
Your vessel is port side to a pier with a spring line led aft from the bow. How will the vessel respond in calm weather, with the engines ahead and hard left rudder?
Why: Going ahead on an after bow spring stops forward motion and pivots the bow toward the pier. Left rudder with the pier to port directs propeller wash to push the stern to starboard, away from the pier.