Use USCG terms like Master, Mate, or Deckhand for 'Position' on CG-719S. Avoid using 'CREW' alone.
You want to put what you did on the vessel using USCG terminology. Master, Mate, Operator, Deckhand and Member of the Engine Department are the most common positions to put in the Served As position on the CG-719S form.

The USCG does not recognize the position "CREW" on it's own, so do not write CREW as your position. It confuses the USCG evaluators as they do not know if you were serving in the Deck Crew or the Engine Crew.
If you are responsible for navigation, cargo, command, and control functions then you are working in the Deck department as a Deckhand as defined by the USCG in 46 CFR § 10.107. You should always write in Deckhand if you were doing this work and you were not serving as the Master, Mate or Operator on the vessel.
If you are in command of a vessel, you are serving as Master. This is defined by the USCG in 46 CFR § 10.107. You should always write in Master if you were the person in charge of the vessel. Captain will work but Master leaves zero room for interpretation by the USCG evaluators.
If you are using mmseas.com and you own the vessel, you can create perfect CG-719S forms inside of the app.
If you are working as a qualified officer in the deck department other than the master you are serving as Mate. This is defined by the USCG in 46 CFR § 10.107. You should always write in Mate working as a qualified officer in the deck department other than the master.
If you are primarily responsible for the main propulsion and auxiliary systems, and other mechanical, electrical, hydraulic, and refrigeration systems, including deck machinery and cargo-handling equipment then you are working in the Engine department as defined by the USCG in 46 CFR § 10.107. You should always write in Member of the Engine Department if you were doing this work and you were not serving as the Master, Mate, Operator or Deckhand on the vessel.

We hope this made your life a little easier and if you have other questions the MM-SEAS team is always here to help!
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Nate Gilman is President and Co-Founder of MM-SEAS. He hawsepiped from the deck to a 3rd Mate Unlimited license with full STCW compliance over more than 15 years at sea, and is a veteran of the NOAA Commissioned Corps. He works directly with the National Maritime Center, USCG-approved training schools, and vessel operators on credentialing policy, and writes on sea service documentation, evaluation standards, and how mariners move up the license ladder.