By Captain Mike · 50 years at sea · former MITAGS faculty
Requirements summarized from 46 CFR Part 12 · September 2026
Requirements summarized from 46 CFR Part 12 · September 2026
Free AB Study Guide / Exam Preparation. This is free study material from Mariners Online. It is not a Coast Guard-approved training course, it does not replace an approved course or the Coast Guard examination, and it does not count as sea service. Mariners Online is not a maritime school and does not sell training. For what the AB, RFPNW and Able Seafarer-Deck endorsements actually require, read AB, RFPNW & Able Seafarer-Deck: What's the Difference? →
What's included
This study guide is built around the topics the Coast Guard tests for AB under 46 CFR 12.405, plus the STCW watchkeeping and survival-craft skills you'll need on a seagoing ship.
12 training modules
Short lessons from nautical terms to watchkeeping, each with clear learning objectives.
Practice quizzes
Every module ends with a quiz that grades itself and explains each answer.
Marlinespike practical
A checklist of the knots, bends, hitches and splices you'll demonstrate for the examiner.
Rules of the Road for ABs
Lights, sound signals and lookout duties, taught the way a helmsman and lookout use them.
Lifeboat Operator prep
Survival craft, launching, and immediate actions — the lifeboat endorsement every AB needs.
Application guide
The forms, medical, drug test and sea-service letters you'll send to the National Maritime Center.
AB requirements at a glance
All AB ratings require you to be at least 18, pass the Coast Guard medical exam and a drug test, speak and understand English, and hold a lifeboat endorsement (46 CFR 12.401).
| Rating | Deck sea service | Where it applies |
|---|---|---|
| AB Unlimited | 18 months (540 days) | Any vessel, any waters. Service on ocean or Great Lakes waters. |
| AB Limited | 12 months (360 days) | Service on vessels of 100 GRT or more. |
| AB Special | 6 months (180 days) | Common starting point for inland and near-coastal work. |
| AB OSV | 6 months (180 days) | Offshore supply vessels. |
| AB Sail | 6 months (180 days) | Service on sailing vessels. |
| AB Fishing Industry | 6 months (180 days) | Fishing industry vessels. |
These are the sea-service times on the current NMC checklist. Congress shortened them in 2023 and made them permanent in December 2025; the text of 46 CFR 12.403 hasn't been updated yet. Details →
Coast Guard-approved training can substitute for up to one-third of the required sea service (46 CFR 12.403). Graduates of approved schoolships have their own service rules.
Lifeboat Operator
Formerly "Lifeboatman." 12 months of sea service, or 6 months plus an approved course. Written or oral exam and a practical demonstration (46 CFR 12.407).
RFPNW (STCW)
Ratings Forming Part of a Navigational Watch. 6 months seagoing service with watchkeeping duties, or approved training plus 2 months. Minimum age 16 (46 CFR 12.605).
Able Seafarer–Deck (STCW)
18 months deck service while holding RFPNW, or 12 months with approved training. Needs survival-craft proficiency (46 CFR 12.603).
The regulations now say "Able Seafarer" and "Lifeboat Operator" in place of the older "Able Seaman" and "Lifeboatman." Always confirm your exact route with the National Maritime Center before you apply.
Training modules
Work through them in order or jump to the topic you need. Tap a module to open the lesson and quiz.
Quizzes passed:0 of 12
1Getting Started: The AB PathRatings, sea time, and how the credential works›
You'll be able to
- Pick the AB rating that fits your sea time and plans
- Count sea service days correctly
- Explain how AB, Lifeboat Operator and STCW endorsements fit together on your MMC
Key points
- Your Merchant Mariner Credential (MMC) carries all your endorsements: national ratings like AB and STCW endorsements like RFPNW.
- A "day" of sea service is generally 8 hours of work aboard. Get signed sea-service letters from every company as you go — don't wait until you apply.
- Many mariners start as Ordinary Seafarer (OS) or deckhand, earn AB Special or AB Limited, and work up to AB Unlimited.
- On seagoing ships you'll also need RFPNW or Able Seafarer–Deck.
2Nautical Terms & Ship ConstructionSpeak the language of the ship›
You'll be able to
- Name the parts of a ship and directions aboard
- Tell list, heel and trim apart
- Use standard terms when reporting
Key points
- Port is left, starboard is right, facing forward. Bow is the front, stern the back; fore and aft run along the ship's length, athwartships across it.
- Draft is the depth of the hull below the waterline; freeboard is the height from the waterline to the main deck.
- Bulkheads are walls, the overhead is the ceiling, the deck is the floor.
- List is a lean caused by weight inside the ship; heel is a lean caused by outside forces like wind; trim is the difference between forward and after drafts.
- Windward is toward the wind; leeward is away from it.
3Compass & HelmsmanshipSteering, wheel commands, and the compass card›
You'll be able to
- Read the compass in degrees and points
- Respond to and repeat standard wheel commands
- Steer a steady course and report correctly
Key points
- The compass card has 360° and 32 points; one point is 11¼°.
- Always repeat the command back, carry it out, and report when it's done: "Right fifteen." … "Wheel is right fifteen."
- "Midships" — rudder amidships. "Meet her" — use rudder to check the swing. "Steady as she goes" — hold the heading she's on when ordered, and report it.
- "Nothing to the left (right)" — don't let the heading fall off to that side.
- Know the engine order telegraph: ahead and astern at dead slow, slow, half and full.
4Rules of the Road for the ABLights, shapes, and sound signals›
You'll be able to
- Identify vessels by their lights
- Recognize maneuvering and fog signals
- Keep a proper lookout (Rule 5) and report what you see
Key points
- Sidelights: red to port, green to starboard, each showing 112.5°. Sternlight: white, 135°. Masthead light: white, 225° forward.
- Short blast ≈ 1 second; prolonged blast 4–6 seconds.
- Maneuvering (Rule 34): 1 short = altering to starboard, 2 short = altering to port, 3 short = operating astern propulsion, 5 or more short = danger/doubt.
- Fog (Rule 35): power-driven vessel making way, 1 prolonged at least every 2 minutes; underway but stopped, 2 prolonged; vessel at anchor, rapid ringing of the bell for about 5 seconds each minute.
- Report other vessels as a bearing in points or relative position: "Light two points on the starboard bow."
5Distress Signals & Emergency CommunicationsRecognize and use distress signals›
You'll be able to
- Recognize the distress signals in Annex IV of the Rules
- Know shipboard alarm signals and your station bill duties
- Report an emergency clearly
Key points
- Distress signals include SOS, "Mayday" by radio, red parachute or hand flares, orange smoke, continuous sounding of a fog signal, flames on the vessel, flags N over C, and slowly raising and lowering outstretched arms.
- EPIRBs transmit on 406 MHz to the satellite system; a SART responds to 9 GHz (X-band) radar.
- General emergency alarm: seven or more short blasts followed by one long blast on the whistle and alarm bells.
- Man overboard: shout "Man overboard, port/starboard side," throw a ring buoy, and keep pointing at the person.
- Your station bill tells you where to go and what to do for each emergency — read it your first day aboard.
6Marlinespike SeamanshipKnots, bends, hitches, and splices — the practical›
You'll be able to
- Tie each practical-exam knot quickly and correctly
- Choose the right knot for the job
- Make eye, short and back splices
Practice checklist
- Bowline — fixed loop that won't slip and is easy to untie
- Clove hitch — quick hitch to a post or rail
- Round turn and two half hitches — secure a line to a ring or spar under load
- Sheet bend — join two lines of different sizes
- Figure eight — stopper knot at the end of a line
- Rolling hitch — grip a line or spar against a lengthwise pull
- Square (reef) knot — tie two ends of the same line together
- Eye splice — a permanent eye in the end of a line
- Short splice — join two lines end to end
- Back splice — keep a line end from unlaying
7Deck OperationsMooring, anchoring, and line handling safety›
You'll be able to
- Name mooring lines and handle them safely
- Assist with anchoring and report chain
- Recognize snap-back zones and other deck hazards
Key points
- Mooring lines: bow line, forward breast, forward spring, after spring, after breast, stern line.
- Never stand in the bight of a line or in a snap-back zone. A parting synthetic line can recoil with deadly force.
- In the U.S., a shot (shackle) of anchor chain is 15 fathoms (90 feet). Report the chain "three shots on deck," "four in the water," and its lead: "Chain leading two o'clock, moderate strain."
- Keep hands clear of bitts, fairleads and the gypsy when line or chain is moving.
- Wear your PPE: hard hat, gloves, safety shoes, and a work vest when working over the side.
8Shipboard Safety & FirefightingFire classes, extinguishers, enclosed spaces›
You'll be able to
- Match fire classes to the right extinguishing agent
- Explain the fire triangle (and tetrahedron)
- Follow enclosed-space entry rules
Key points
- Fire needs heat, fuel and oxygen, plus a chain reaction. Remove one and the fire goes out.
- U.S. classes: A ordinary combustibles, B flammable liquids and gases, C energized electrical, D combustible metals, K cooking oils and fats.
- Water cools Class A fires; foam smothers Class B; CO₂ or dry chemical for Class C — never water on live electrical equipment.
- Never enter an enclosed space without a permit, atmosphere testing, ventilation and a standby person. Most enclosed-space deaths are would-be rescuers.
9Pollution PreventionDischarge laws, placards, and reporting›
You'll be able to
- State what can and can't go over the side
- Recognize required oil and garbage placards
- Report a spill correctly
Key points
- Discharging plastic into the sea is prohibited everywhere (MARPOL Annex V).
- Vessels 26 feet and over must post an oil discharge placard and a garbage placard; vessels 40 feet and over with a galley and berthing need a written waste management plan.
- Report any oil or hazardous substance discharge to the National Response Center: 1-800-424-8802.
- During fueling or transfers, keep scuppers plugged and spill kits ready, and stop the transfer at the first sign of a leak.
10Lifeboat Operator & Survival CraftLaunching, liferafts, and survival›
You'll be able to
- Launch and take charge of a lifeboat or liferaft
- Carry out immediate actions after abandoning ship
- Use survival craft equipment and signals
Key points
- Liferaft hydrostatic release units free the raft automatically as the ship sinks, typically at 2–4 meters depth. The weak link then lets the painter part.
- Immediate actions in a liferaft: Cut the painter, Stream the sea anchor, Close the entrances, Maintain the raft.
- No drinking water for the first 24 hours except for the sick or injured; then ration.
- Practice donning an immersion suit — it should take two minutes or less.
- Know your lifeboat's release gear, engine start, and rowing commands for the practical.
11Watchkeeping (RFPNW / Able Seafarer–Deck)STCW lookout and helm duties›
You'll be able to
- Stand a proper lookout and make reports
- Relieve and hand over a watch
- Meet the STCW competence tables (A-II/4 and A-II/5)
Key points
- The lookout's job is sight and hearing only — report every light, vessel, buoy and hazard, even if you think the mate already sees it.
- Report by bearing: "Ship two points on the port bow," or relative bearing in degrees.
- Never leave lookout until properly relieved; your relief must have night-adjusted eyes.
- Your assessor will sign off each task in your RFPNW or Able Seafarer–Deck assessment record — keep it with your sea-service letters.
12Exam Day & Practical AssessmentWhat to expect at the REC or approved course›
You'll be able to
- Know which exam modules your approval letter lists
- Prepare for the knot and lifeboat practicals
- Avoid the common reasons applications are delayed
Key points
- After the NMC evaluates your application, you'll get an approval-to-test letter listing your exam modules. Bring it and photo ID to the Regional Exam Center.
- The AB exam is in English and covers deck general knowledge, safety, and Rules of the Road; practicals cover knots, bends, splices and hitches.
- An approved AB course can test you in class and substitute for the REC exam — check that the course's approval covers your rating.
- Top delays: missing sea-service details, an expired medical, and unsigned forms.
Application checklist
Have these ready, then apply to the National Maritime Center through Navita, the Coast Guard's online credentialing system.
- Application for MMC (Form CG-719B)
- Medical certificate application (Form CG-719K), completed by your medical practitioner
- Drug test result or periodic testing letter (Form CG-719P)
- Sea-service letters or Small Vessel Sea Service Form (CG-719S) for every vessel
- Lifeboat Operator course certificate or proof of sea time, and any approved AB course certificate
- STCW assessment records for RFPNW or Able Seafarer–Deck, if applying for those
- Fees paid
This course page is a study aid. Requirements are summarized from 46 CFR Part 12 (sections 12.401–12.407, 12.603 and 12.605) and can change; confirm current rules and forms with the U.S. Coast Guard National Maritime Center before you apply.
Where this fits in your journey
Which NVIC and approved course apply to me?What training do I need, and where?What comes after AB?What exams must I pass?
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