It’s very, very important how large the boat is and whether it’s going to be moored while you play. I don’t like to play on boats because it makes me queasy to watch my strings sway while I play, but I knew someone whose concert grand went for a swim. She foolishly took a job on a pontoon boat that would be sailing around during the event, and a large cigarette-type boat came roaring by. The wake caused her harp to fall, and of course it fell into the water.
You want to ask a lot of questions before you commit to a job on a boat.