Sea Service › What Counts as Sea Time?
Checked against 46 CFR 10.107, 10.232 and CG-MMC Policy Letter 02-25 · October 2026
The short answer
- Sea time (the Coast Guard calls it sea service) is the documented time you've worked aboard vessels. Almost every credential above entry level needs it.
- A day isn't just a date on the calendar. The National Maritime Center (NMC) checks how long you worked, on what vessel, on what waters, in what job, how recently, and whether you can prove it.
- The same day can count fully toward one endorsement and only partly, or not at all, toward another.
- The fix is simple: keep your own record of every trip, and get a proper letter every time you sign off.
The six questions
1. Was it a full day?
A day is 8 hours of watchstanding or day work, not counting overtime. On vessels under 100 GRT the Coast Guard may accept as little as 4 hours. A 12-hour day counts as 1½ days only on vessels authorized to run a two-watch system. You can never claim more than one day for one calendar day, except under that 1½-day rule. The Coast Guard counts a month as 30 days and a year as 360. 46 CFR 10.107 46 CFR 10.232
2. On what size vessel?
Many endorsements need some or all of the time on vessels above a certain gross tonnage (GRT). Lots of days on small boats can still leave you with a lower-tonnage endorsement. Vessel Tonnage & Your License →
3. On what waters?
Your route matters: oceans, near-coastal, Great Lakes, or inland. For ocean and near-coastal endorsements, inland time often counts for only part of the total. For example, Master 100 GRT Near Coastal lets inland time cover up to half the days. Master 100 Ton →
4. In what job?
The department and position must match what the endorsement asks for: deck time for deck ratings and licenses, engine time for engine ones. Some upgrades require time in a specific position, such as watch officer or First Assistant Engineer. Where the rules allow, time in the rank below counts two days for one. Deck Officer Ladder → Engine Officer Ladder →
5. How recent is it?
Officer endorsements also need some recent service. The regulation describes 90 days within the past 3 years, but CG-MMC Policy Letter 02-25 (September 2025) allows 7 years for many national officer endorsement transactions. Check the NMC checklist for your application. Example: OUPV →
6. Can you prove it?
If it isn't on paper, it doesn't count. Company time needs a sea-service letter or discharge showing the vessel, dates, position, route and tonnage. Time on small vessels is often shown on the CG-719S form, one vessel per form. Time on your own boat needs proof of ownership. Documenting Sea Time →
Quick reference
| Situation | How it usually counts |
|---|---|
| 8-hour working day aboard | 1 day |
| 4 to 8 hours on a vessel under 100 GRT | May count as 1 day |
| 12-hour day, vessel authorized for two watches | 1½ days, if the letter says so |
| 12-hour day on a normal three-watch ship | 1 day |
| Time in the rank below, where allowed | 2 days for 1 |
| Time on your own boat (under 200 GRT) | Counts if you document it and prove ownership |
| Approved training in place of some service | Only what the course approval says. Confirm in writing before you pay. |
General guide only. The requirements for your exact endorsement are in its NMC checklist.
Special cases
- Military sea service. Navy, Coast Guard and other military time can count, depending on the vessel, your duties and how it's documented. Military Sea Service →
- Maritime academy cadets. Academy programs build sea time and training into the curriculum. Academy route →
- Approved courses. Some Coast Guard-approved courses substitute for part of the sea service, for example up to one-third for AB. The credit belongs to the specific course approval. AB example →
- Mixed deck and engine work. If you split your time, the letter must break out the days in each department.
Common mistakes
- Claiming time-and-a-half on a three-watch ship. Those days count one for one.
- Counting calendar months instead of working days. Days off and days ashore don't count.
- Forgetting tonnage and route on letters. Without them, the evaluator can't credit the time properly.
- Relying on a company to have your records years later. Companies get sold and people move on.
- Rounding up casual trips on your own boat. Overstating days invites a closer look at everything else you claim.
Write it down the day it happens: vessel, official number, tonnage, route, position, hours and watch system. Five minutes after each trip saves months at application time.
Next step: Use the Sea-Time Calculator → Get the sea-service letter template →
Official sources
FREE DOWNLOAD · OCTOBER 2026 EDITIONWho’s Hiring? Maritime Employer Directory
76 maritime employers and 62 union hiring halls in one printable PDF: phone numbers, careers pages, a hall map and job call times. Free when you join From the Bridge, Captain Mike's monthly email: rule changes, sea-time tips and new guides, in plain English. One email a month. Unsubscribe anytime.
Sent with Kit. Your email is used only for the directory and this monthly note. See the Privacy Policy.