- What the Credential Actually Is
- Who Issues It and How the Exam Is Administered
- The Ten Exam Modules at a Glance
- Why Your Route Decides Your Modules
- Rules of the Road and Deck General
- Deck Safety and Stability Problems
- Navigation Modules and Chart Plot
- Who Hires Holders of This Endorsement
- Sequencing Your Preparation
- Common Misreadings to Avoid
- Frequently Asked Questions
- USCG-CM-UNL here means the National Chief Mate Unlimited, Oceans or Near Coastal, endorsement issued through the USCG National Maritime Center.
- The exam draws on ONC01 modules Q100 through Q109, but not every candidate sits all ten.
- Q105 and Q106 are route alternatives: Near Coastal candidates take Q105, Oceans candidates take Q106.
- Your USCG approval-to-test, not a study guide, determines exactly which modules you are assigned.
What the Credential Actually Is
When mariners ask "what is a USCG-CM-UNL," they are asking about the National Chief Mate Unlimited, Oceans or Near Coastal credential. It is a United States Coast Guard officer endorsement for the second-in-command of large ocean-going and coastal vessels, the officer who typically runs cargo operations, deck maintenance, safety management, and the navigational watch while ultimately answering to the Master.
"Unlimited" refers to tonnage: the endorsement is not capped at a vessel size, which is why it matters for tankers, container ships, bulkers, and large offshore and government-contracted vessels. The "Oceans or Near Coastal" designation describes the route for which the endorsement is issued. That route distinction is not cosmetic. As you will see below, it directly changes which examination modules a candidate must pass.
This page is a plain-language orientation. If you want a deeper treatment of the same question from other angles, see our related explainers: What Is USCG-CM-UNL?, USCG-CM-UNL Meaning, and What Does USCG-CM-UNL Stand For?
Who Issues It and How the Exam Is Administered
The governing body is the United States Coast Guard National Maritime Center (NMC). The NMC evaluates mariner applications, approves candidates to test, and publishes the examination module structure for each endorsement. For this credential, the published structure is the ONC01 examination for Oceans or Near Coastal endorsements, with the Chief Mate module series running from Q100 through Q109.
A few mechanics are worth understanding up front:
- Approval-to-test comes first. You do not simply pick modules. The Coast Guard's approval-to-test determines which modules are assigned to you.
- Module topics are unweighted. The official topic lists describe what each module covers, but they do not publish percentage weights. Do not trust any source that claims precise domain percentages for this exam.
- Fees and scheduling run through the Coast Guard process. Rather than quoting figures here, check current NMC fee schedules and your application paperwork. For a broader view of expenses, see USCG-CM-UNL Certification Cost 2026, and for timing, USCG-CM-UNL Exam Dates 2026.
For eligibility and sea-service prerequisites, our guide to USCG-CM-UNL Requirements 2026 goes into more detail than we can here.
The Ten Exam Modules at a Glance
The published ONC01 Chief Mate module series is below. Think of it as a menu, not a mandatory ten-course meal.
| Module | Title | Core Focus |
|---|---|---|
| Q100 | Rules of the Road - International and Inland | COLREGS, Inland Rules, safe watchkeeping |
| Q101 | Deck General Part I | Maneuvering, pilot stations, maritime law, shipboard management |
| Q102 | Deck General Part II | Watchkeeping principles, 33 CFR 164, cargo handling and stowage |
| Q103 | Deck Safety | Stability concepts, damage, fire, abandon ship, lifesaving, SAR |
| Q104 | Deck Safety/Stability Problems | Trim, stability, damage stability, stress calculations |
| Q105 | Navigation General - Near Coastal | Piloting, charts, compasses, weather, tides |
| Q106 | Navigation General - Oceans | Near Coastal topics plus nautical astronomy and celestial navigation |
| Q107 | Chart Plot | Chart fixes, dead reckoning, electronic navigation |
| Q108 | Navigation Problems - Near Coastal | Ocean track, ETA/fuel, piloting and tide calculations |
| Q109 | Navigation Problems - Oceans | Great-circle and middle-latitude sailing, celestial calculations |
For a domain-by-domain walkthrough, see USCG-CM-UNL Exam Domains 2026: Complete Guide to All 10 Content Areas.
Why Your Route Decides Your Modules
This is the single most misunderstood feature of the credential, and it is the reason a careless study plan wastes weeks.
Q105 and Q106 are route-related alternatives. Q105 covers Near Coastal navigation topics. Q106 covers the same general territory but adds nautical astronomy, celestial navigation, Polaris, star identification and selection, and meridian transit. Similarly, Q108 is the Near Coastal navigation problems module, while Q109 is the Oceans version, adding middle-latitude, great-circle, and parallel sailing, celestial fixes, and times of sunrise, sunset, and twilight.
Rules of the Road and Deck General
Q100: Rules of the Road - International and Inland
Covers both COLREGS and the Inland Rules, plus the judgment behind safe watchkeeping. Candidates must be able to apply the rules to situations, not merely recite them.
- Know where International and Inland rules differ, since confusing the two is a classic trap.
- Practice applying right-of-way, lights, shapes, and sound signals to scenario-style questions.
- Link rules knowledge to watchkeeping behavior, since the module explicitly includes safe watchkeeping.
Q101: Deck General Part I
A broad management-and-seamanship module touching vessel handling, law, and people.
- Maneuvering and handling, including pilot stations and operating in rivers, estuaries, and shallow water.
- Maritime law and credentialing.
- Shipboard management and personnel training, reflecting the Chief Mate's role running the deck department.
Q102: Deck General Part II
Shifts toward watchkeeping principles, regulatory navigation safety, and cargo.
- Basic principles of watchkeeping.
- Navigation safety requirements under 33 CFR 164.
- Cargo handling and stowage, a central Chief Mate responsibility.
Deck Safety and Stability Problems
Q103 and Q104 form a pair, one conceptual and one computational. Candidates who treat them as a single block tend to prepare more coherently.
Q103 Deck Safety: the conceptual side
This module spans construction, stability, trim, and damage; grounding, refloating, collision, and temporary repairs; passenger safety; fire and abandoning ship; emergency steering; lifesaving rules and operation; and search and rescue, including AMVER and IAMSAR. It reads like a catalog of the situations a Chief Mate is expected to manage when something goes wrong.
Q104 Deck Safety/Stability Problems: the calculation side
Q104 turns the concepts into numbers: trim, stability, damage stability, and stress calculations. Fluency here comes from repetition on worked problems, because understanding the theory is not the same as producing a correct answer under time pressure.
Key Takeaway
Study Q103 and Q104 together. Read the concept in Q103, then immediately work the matching calculation type from Q104. The pairing builds both understanding and speed.
Navigation Modules and Chart Plot
Navigation is where route choice matters most, and where candidates most often over- or under-prepare.
- Q105 (Near Coastal general): piloting, distances, bearings, fixes, charts, dead reckoning, instruments, aids, publications, notices to mariners, magnetic and gyro compass error correction, azimuth and amplitude, terrestrial fixes, meteorology, weather, ocean currents, tides, and safe watchkeeping.
- Q106 (Oceans general): the relevant piloting, charts, compass, weather, tides, and watchkeeping material, plus nautical astronomy, celestial navigation, Polaris, fixes, star identification and selection, and meridian transit.
- Q107 (Chart Plot): piloting, chart fixes, dead reckoning, electronic navigation, instruments, aids, and publications, applied directly on the chart.
- Q108 (Near Coastal problems): ocean track and Mercator sailing, ETA, speed, RPM, and fuel calculations, electronic navigation and piloting, compass corrections, and tide calculations.
- Q109 (Oceans problems): ocean track, middle-latitude, Mercator, great-circle, and parallel sailing; ETA; celestial, Polaris, and meridian fixes; star selection; times of celestial phenomena and zone time; sunrise, sunset, and twilight; compass azimuth and amplitude; and tides.
Notice that the "general" modules test knowledge while the "problems" modules test worked solutions. Chart Plot is its own skill: accurate plotting with disciplined technique.
Who Hires Holders of This Endorsement
An unlimited Chief Mate endorsement opens doors across the large-vessel segments of the U.S. maritime industry. Typical employers and sectors include:
- Deep-sea tanker, container, and dry-bulk operators.
- Offshore support and energy-sector operators running larger vessels.
- Government-contracted and sealift-related fleets.
- Unionized deep-sea and U.S.-flag operators that crew licensed deck officers by endorsement and seniority.
Whether a particular employer weights the Oceans or Near Coastal route differently depends on its trade pattern, so check the job posting's stated endorsement requirements. For a closer look at roles and employers, see USCG-CM-UNL Jobs, and for compensation context, the USCG-CM-UNL Salary Guide 2026. If you are weighing the investment, Is the USCG-CM-UNL Certification Worth It? frames the decision.
Sequencing Your Preparation
Generic study habits matter less here than the order in which you tackle the modules. One sensible sequence, assuming a full set of modules, ties each phase to specific content:
Rules and regulatory foundation
- Start with Q100, since the Rules underpin watchkeeping questions everywhere else.
- Pair with the 33 CFR 164 material from Q102.
Safety concepts, then calculations
- Work Q103 and Q104 together.
- Add Q101 and the cargo portions of Q102 for management and stowage context.
Navigation general, then chart work
- Cover Q105 or Q106 according to your route.
- Move to Q107 and practice plotting by hand.
Navigation problems and review
- Drill Q108 or Q109, whichever your route assigns.
- Finish with mixed-module review and weak-area repair.
For a full preparation framework, read the USCG-CM-UNL Study Guide 2026, and keep the USCG-CM-UNL Cheat Sheet handy for last-mile review. You can also test yourself on realistic questions with our USCG-CM-UNL practice tests.
Common Misreadings to Avoid
- Assuming all ten modules apply to everyone. They do not. Your approval-to-test controls assignment.
- Studying Oceans-only content "just in case" on a Near Coastal route. It spends time you need elsewhere, though knowing it does no harm if you have spare capacity.
- Importing Master rules. Master-level eligibility details do not belong in Chief Mate preparation.
- Trusting invented weightings. Because the topics are unweighted, any source quoting exact domain percentages is guessing.
- Neglecting the problem modules. Concept fluency without calculation practice is the usual reason strong mariners stumble.
If you want an honest read on difficulty and outcomes, see How Hard Is the USCG-CM-UNL Exam?, USCG-CM-UNL Passing Score, and USCG-CM-UNL Pass Rate. When you are ready to measure your readiness against exam-style material, start from the main practice test site.
Frequently Asked Questions
On this site it refers to the National Chief Mate Unlimited, Oceans or Near Coastal, endorsement issued through the U.S. Coast Guard National Maritime Center. It is a deck officer credential, not a different certification that happens to share similar letters.
The United States Coast Guard National Maritime Center. It publishes the ONC01 module structure and approves candidates to test, and that approval determines the modules you are assigned.
Not necessarily. Q105 and Q106 are route alternatives, and the Near Coastal route does not require the Oceans-only Q109. Your actual USCG approval-to-test controls which modules you sit.
The official ONC01 module topics are unweighted, so no published percentage split exists. Prepare each assigned module across its full scope instead of chasing a supposed weighting.
Q105 is Near Coastal navigation general knowledge. Q106 is the Oceans version and adds nautical astronomy, celestial navigation, Polaris, star identification and selection, and meridian transit on top of the shared piloting, compass, weather, and tide topics.
Understanding exactly what this credential is, and which modules your route actually requires, is the foundation for everything that follows. Confirm your assignment, build your plan around the modules you will really sit, and keep your preparation anchored to the official topic lists rather than rumor.