GPT doesn't know what it is, OS seaman, ordinary seaman abab seaman/first-class seaman, or QM quarter main duty seaman SAB/SQ senior AB/senior quarter master is a senior seaman or carpenter. Many companies don't offer this position. Sun Bo Sun Bo/Shuitou D/CT deck student deck strap E/CT engine room student cabin strap 3/O 3 first mate 2/O 2 second mate C/ O (one of the four captains on board) Captain/Captain (commonly known as Lao K) The first mate on deck is called the first mate, and the first mate in the engine room is called the engineer.