Documenting Sea Time Without Rejection

By Captain Mike · 50 years at sea · former MITAGS faculty
Checked against 46 CFR 10.107 and 10.232 · September 2026

New to sea time? Start with the six questions the Coast Guard asks about every day you claim. What Counts as Sea Time? →

Few things stall a Merchant Mariner Credential application faster than poorly documented sea service. You might have 500 hard days on the water, but if your paperwork doesn't show what the evaluators need, the NMC will put your application in Awaiting Information (AI) status or decline to credit the days.

Sea service is reviewed during the NMC's professional qualification evaluation, and the rules are in 46 CFR 10.232 and the definitions in 46 CFR 10.107. Here's how days are counted, how to document your own boat, and what every company letter should include.

What actually counts as a “day”?

Situation	How it is credited
Standard day	8 hours of watchstanding or day-working, not counting overtime.
Vessels under 100 GRT	Still 8 hours, unless the Coast Guard decides the vessel’s operating schedule makes that inappropriate. In no case less than 4 hours. This is why small-boat applicants can often log shorter days.
12-hour days on a two-watch vessel	On vessels authorized by 46 U.S.C. 8104 to operate a two-watch system, a 12-hour working day may be credited as 1½ days.
Any vessel	Never more than one calendar day of service claimed for a single calendar day, except under the 1½-day rule above.

Say it in the letter. The 1½-day credit only works if the evaluator can see it applies. If the letter just says “employed from May to August,” expect the time to be counted one-for-one. Make sure it states the 12-hour schedule and the two-watch system.

The owner-operator trap: logging your own boat

If you own a vessel under 200 GRT, you may attest to your own service, as long as you provide proof of ownership. 46 CFR 10.232(a)(4) This is common for charter and fishing captains, dive and guide operators, and boaters building time toward OUPV or Master 25/50/100 GRT. Boater to captain →

Self-signed time gets a close look, and a signed form without proof of ownership won't be credited. What to submit:

Small Vessel Sea Service Form (CG-719S)

Complete every block, including the days underway for each month and year. Sign as the owner.

Proof of ownership

Documented vessels: the Certificate of Documentation showing you as owner. State-registered vessels: the state registration or title. A bill of sale on its own is weak evidence; back it with the registration.

Supporting records, if asked

If you claim an unusually high number of days, such as 300 underway days in a year on a recreational boat, be ready to back it up with logbooks, fuel and maintenance receipts, or marina records showing the boat was actually in use.

Someone else's boat? You can't sign for yourself. The owner, operator, or master must sign your CG-719S or a service letter, and include proof of the vessel's registration or documentation.

What a company sea-service letter must include

When you work for a towing company, ferry line, offshore operator, or fleet, the office usually writes your letter. Don't assume it's right. A missing detail means chasing the office for a corrected letter while your application sits. Check for these items before you submit:

#	Item	Why it matters
1	Company letterhead, date, and signature of the owner, operator, master, or chief engineer (or an authorized company official)	Shows who is vouching for the service.
2	Your full legal name and USCG mariner reference number	Matches the letter to your application.
3	Vessel name, as it appears on the documentation	Required by 10.232(a)(2).
4	Official number (USCG official number or state registration number)	Required by 10.232(a)(2).
5	Gross tonnage, marked GRT or GT, from the COD or COI	Sets the tonnage limit on your license. Tonnage explained →
6	Propulsion mode and power (motor, steam, gas turbine, or sail; horsepower or kW)	Required by 10.232(a)(2); matters for engineering horsepower limits.
7	Capacity served (deckhand, AB, mate, master, oiler, QMED, etc.)	Service must be in the right capacity for the endorsement.
8	Dates of service for each vessel	Required by 10.232(a)(2).
9	Days of service, broken down by vessel if the letter covers more than one	Employment dates alone are not days of service.
10	Waters navigated (Inland, Great Lakes, Near Coastal, or Oceans)	Sets your route. “Gulf Coast” or “various” invites a request for more information.
11	Hours worked per day (8-hour or 12-hour days, and any two-watch system)	Needed for the 1½-day credit.

Depending on the endorsement, the letter may also need to show radar use, towing experience, or watchkeeping supervision. Check the NMC checklist for your endorsement.

Sample sea-service letter (copy and paste)

Give this to your employer or port captain so nothing is left to chance.

[COMPANY LETTERHEAD]
[Street Address, City, State, ZIP]
[Phone Number | Email Address]

Date: [Month Day, Year]

To: National Maritime Center (NMC)
Subject: Verification of Sea Service (46 CFR 10.232)

Mariner Name: [Full Legal Name]
Mariner Reference Number: [USCG Reference Number]

This letter certifies that the mariner named above served aboard
the vessel(s) operated by [Company Name] as detailed below:

1. Vessel Name: [Vessel Name]
2. Official Number: [USCG Official Number or State Registration Number]
3. Gross Tonnage: [e.g., 185 GRT]  (state GRT or GT)
4. Propulsion / Power: [e.g., Motor (Diesel), 3,200 HP]
5. Capacity Served: [e.g., Able Seafarer (AB) / Deck Watchstander]
6. Period of Service: [Start Date] to [End Date]
7. Actual Days of Service: [Number] days
8. Waters Navigated: [Inland / Great Lakes / Near Coastal / Oceans]
9. Daily Work Schedule: [e.g., 12 hours per day under a two-watch
   system authorized by 46 U.S.C. 8104]  or  [8 hours per day]
10. Radar (if applicable): [Vessel equipped with radar; mariner
    used it routinely for navigation and collision avoidance]

I certify that the foregoing sea service information is true and
correct and is taken from official company logs and employment
records.

Sincerely,

______________________________
[Signature]
[Printed Name of Signer]
[Title: Owner / Operator / Master / Chief Engineer / Port Captain]
[Company Name]
[Contact Phone Number]

Want a simpler narrative version? Sea-Service Letter Builder →

Final check before you submit

Three things evaluators catch

Both sides scanned? If you're using discharges or shipping articles, submit clear scans of both sides.
Do the numbers add up? A letter covering 365 calendar days can't claim 366 days of service.
Is the route specific? Never accept “various” or “East Coast.” Ask for the water designation: Inland, Great Lakes, Near Coastal, or Oceans.

Captain's Tip

Get a sea-service letter every time you leave a vessel or company, not when you're ready to apply. Companies merge, offices close, and the port captain who knew you retires. A letter in hand today is worth more than a promise later.

Official sources

Where this fits in your journey

Build a sea-service letter Estimate my sea time What tonnage does my service support?All credentialing resources