Sea service days are used to measure a mariner’s lifetime experience on boats, whether recreational, commercial, or military. Your documented sea service days accumulate over your lifetime as a mariner.
It's your responsibility to track your documented sea days with a CG-719S Small Vessel Sea Service Form for vessels under 200 GRT.
See 46 CFR 10.232 for documenting your sea service on any vessel over 200 GRT.
Every day that you are serving on a vessel in an assigned position in the Deck or Engineering department where you worked for more than 4 hours is a sea day.
A “day” as defined by 46 CFR §10.107 is dependent on the tonnage of the vessel.
For vessels over 100 GRT a “day” is 8 hours of watch-standing or day-working, not to include overtime. For vessels under 100 GRT you must be underway for at least 4 hrs in a day for it to count as a “day”.
Whether you're sailing a 1000 ft tanker, 209 ft research boat, or your 14 ft sailboat, a sea day is a sea day. For the person on the tanker and the research boat it means the day they report and the day they depart as long as they work 8 hours they receive one “day” of sea day credit.
This also means that you get a “day” of sea day credit when you're taking your small sailboat out for over 4 hours.
There are a few very special vessels which are listed in 46 U.S.C. 8104 and 46 CFR 15.705, who are authorized to operate a two-watch system, a 12-hour working day may be creditable as 1.5 “days” of service only on those vessels.
Additionally, if you're part of a crew on a vessel that follows the Coast Guard authorized six-on-six-off watch system, and there are just two officers taking turns (like on certain crew boats, supply boats, towboats, and some commercial fishing boats), you can count 1 1/2 days for each 12-hour day worked.
For more information you can refer here or you can understand sea service requirements for a Merchant Mariner Credential through specialized USCG software tools like MMSeaS.
These days never expire, and you can "reuse" them as you apply for your licenses and additional endorsements.
For example, you need 540 sea days to qualify as an Able Seaman Limited. Those 540 days still count towards the 1080 days required for Able Seaman Unlimited.
Towing vessels and Barges who are engaged on a voyage of less than 600 miles and the licensed individuals and crew members are divided, when at sea, into at least 2 watches can receive time and a half credit for every sea day they work 12 hours.
Offshore Supply Vessels that are at least 6,000 gross tons who are engaged on a voyage of less than 600 miles, and the licensed individuals and crew members are divided, when at sea, into at least 2 watches can receive time and a half credit for every sea day they work 12 hours.
Fish Processing Vessels who entered into service before January 1, 1988, and are more than 1,600 gross tons and the licensed individuals and crew members are divided, when at sea, into at least 2 watches can receive time and a half credit for every sea day they work 12 hours.
Fish Processing Vessels who entered into service after December 31, 1987, and has more than 16 individuals on board primarily employed in the preparation of fish or fish products and the licensed individuals and crew members are divided, when at sea, into at least 2 watches the licensed individuals and crew members can receive time and a half credit for every sea day they work 12 hours.
If you're a cadet sailing on a training ship furnished by the Maritime Administration under 46 CFR 310.4, a day may be creditable as 1.5 days of service.
There are many examples of companies and government agencies (especially the NOAA Fleet) issuing sea service letters with 12 hr days when it's not authorized. The USCG National Maritime Center will typically only give the mariner one sea day for each day worked no matter what the letter says.
We encourage mariners to be realistic and understand the rules that they are working with. We would never want a mariner to have obtained a license they were not qualified for due to illegal paperwork from their employers and mistakes by the evaluators at the USCG National Maritime Center.
To document sea service:
For vessels less than 200 GRT:
For vessels over 200 GRT:
If you still have any doubts about documenting your sea service or require further clarifications, you can refer to 46 CFR 10.232.
And if you’re trying to understand sea service days for your license renewal, then you can read about it in detail in our USCG License Renewal guide.
We hope this made your life a little easier and if you have other questions the MM-SEAS team is always here to help!
No matter what, when you are ready to submit your application, you can choose to have the MM-SEAS staff create a perfect application, handle the USCG application fees and work with the USCG on your behalf to resolve any issues for a flat fee of $299 or you can choose to submit on your own.
Pro MM-SEAS members get access to unlimited live 1 on 1 calls with one of our USCG Licensing Specialists. We've found that answering questions live with screen sharing in a video call makes both of our lives easier. Pro MM-SEAS members can access these features inside of MM-SEAS under License Guidance.
Nate has over 15 years of professional maritime experience and has hawsepiped his way to a 3rd Mate Unlimited Endorsement with full STCW compliance. He is proud veteran of the NOAA Commissioned Corps.