How to log sea time for a captain's license
Log every trip on the day you make it (date, vessel number and tons, waters, hours underway, role); on a boat under 100 gross tons a day counts once you are underway 4 hours.
Record the vessel's official or state number and gross tons, and the waters as inland, Great Lakes, near coastal or ocean. Each calendar day counts once. At application time the days are totalled per vessel, by year and month, onto a sea service form or letter that the owner or operator signs.
Keep a sea time log in seven steps
These steps work with a paper logbook, a spreadsheet or the sea time log on this site, which applies the day rule for you.
- Write down each vessel once. Its name, the official number from the documentation or the state registration number, its gross tons if it has them, length, propulsion, and the body of water you use it on. The form needs all of this for every vessel, and a made up number gets the form rejected.
- Log the trip the same day. Date, vessel, waters and the hours you were actually underway. Do not round up and do not guess later: the person who signs your form is certifying the numbers.
- Record what you served as. Master, mate, operator or deckhand. The crediting guidance lists writing owner as the position as a common error, and crew alone does not name a position.
- Note the waters by the boundary line. Inland is shoreward of the boundary line, near coastal and ocean are seaward of it, and the Great Lakes are their own category. Near coastal days are the scarce ones for most recreational boaters.
- Keep one date to one vessel. If you were on two boats on one day, only one of them can claim that day. Pick the one you spent longer on.
- Total each vessel by year and month. The small vessel sea service form has a block per month with the year and the number of days, plus totals for Great Lakes, shoreward and seaward days. One form covers one vessel and at most five years.
- Get the right person to sign. On a vessel you own and that is under 200 GRT you may attest to your own service with proof of ownership. On anyone else's boat the owner, operator or master signs for you.
What to record for every trip
Service is documented per vessel, so the log is really a list of vessels with dated days under each. The regulation on documenting sea service asks for the vessel's name and official number, its gross tonnage, its propulsion, what you did aboard, the dates of service and the routes, which is where the waters come in (46 CFR 10.232(a)(2)). Anything you do not write down now you will have to reconstruct later from memory, fuel receipts and photos, and the person signing may not agree with your reconstruction.
| Field | Why |
|---|---|
| Date | Each calendar day is counted once. |
| Vessel, number, gross tons | One form per vessel; tonnage sets the day length and your tonnage limit. |
| Waters | Near coastal, Great Lakes and inland days are totalled separately. |
| Hours underway | A day on a boat under 100 GRT needs 4 hours. |
| Role | The form's Served As box: master, mate, operator, deckhand. |
| Notes | Where you went and who was aboard, so the signer can check it. |
How the days add up
A month is 30 days and a year is 360 days when service is counted (46 CFR 10.107). So the 12 months for an OUPV are 360 days and the two years for a near coastal Master are 720. Days do not expire: the crediting guide says sea service counts from age 16 and never expires. What does have a clock is recent service, 90 days within the years before you apply, which the OUPV and Master guide explains.
Worked example: what a log turns into
A boater logs 438 days over ten years on one 8 GRT boat, mostly inland, with 47 near coastal days in 2018 and 78 days in 2020. Counted by this site's engine as of 27 September 2026, the near coastal OUPV line reads: needs 43 more near coastal or ocean days; 12 recency days short.
The total is well past 360, but only 47 of the days are near coastal against the 90 the section asks for, and only 78 fall in the 7 years before the count date (0 in the last 3). A log that only kept a running total would never have shown either gap.
Common mistakes
- Keeping one running total instead of days per vessel per month. The form wants the breakdown.
- Logging trips weeks later from memory, and rounding 3.5 hours up to a day.
- Claiming the same date on two vessels.
- Writing owner in the Served As box.
- Forgetting the official or state number, or inventing one from a hull number.
- Not noting which days were seaward of the boundary line.
Count your own days
The log applies the day rule to every trip as you enter it, one day per calendar day, and the progress page shows your totals by waters against each credential's published numbers. Everything stays in this browser.
Frequently asked questions
Can I use a spreadsheet instead of an app?
Yes. The form only needs the totals per vessel per month and the backing detail if you are asked. A spreadsheet works if you keep one row per trip with the date, vessel, waters and hours, and you total it the same way this guide describes.
How far back can I claim sea time?
The crediting guidance says sea service counts from the day you turn 16 and does not expire. You do need some recent service as well, and you need records good enough for someone to sign for.
Does this site decide whether I qualify?
No. It counts your logged days against the published numbers and cites the section. Sea Time Ledger does not determine eligibility; the credentialing authority decides.
Sources
Last reviewed 27 September 2026 against:
- 46 CFR 10.232, Sea service, Electronic Code of Federal Regulations, current text, up to date as of 24 September 2026, read 27 September 2026. Used for: What service documentation must show, owner attestation, the day definition.
- 46 CFR 10.107, Definitions in subchapter B (Day, Month, Year, Near-coastal, Inland waters, Great Lakes), Electronic Code of Federal Regulations, current text, up to date as of 24 September 2026, read 27 September 2026. Used for: Month and year as 30 and 360 days.
- Sea Service (crediting sea service, what counts as a day, completing the small vessel sea service form), National Maritime Center, dated 12 August 2024, read 27 September 2026. Used for: Sea service from age 16 never expires; common errors on the small vessel form.
This guide is our own summary of the published documents, not legal advice and not a finding about your eligibility; the credentialing authority decides. If it disagrees with the current documents, the documents win. Sea Time Ledger is not affiliated with, endorsed by, or connected to the United States Coast Guard, the National Maritime Center or any other government body.