So, not knowing the whole story here, I'd love to hear how the "first mate" in this story feels about things. By the way, you ought to call him "Chief Mate" since Gilligan was the last "first mate" I ever heard of, unless I count my first sexual partner.
Here's a little joke to put things in perspective. If you continue in this relationship, you can expect to have this occur 15 or 20 years down the road. It's happened to most of us men in this industry:
A husband, who has six children, begins to call his wife “mother of six” rather than by her first name. The wife, amused at first, chuckles. A few years down the road, the wife has grown tired of this. "Mother of six," he would say, "what’s for dinner tonight? Get me a beer!" She gets very frustrated. Finally, while attending a party with her husband, he jokingly yells out, "Mother of six, I think it's time to go!" The wife immediately shouts back, "I'll be right with you, father of four!"
Anyhow, my advice to you would be to not get yourself all worked up about what might be, and instead focus on what is. If he's worth it, and you can keep your pants on when he's sailing, then go for it. Otherwise move along.
Love and kisses,