One of my favorite settings in a D&D game is the ship. Working it in correctly can be a little tricky. It's not hard to shoe horn in a place where the party needs to sit on a boat and take care of a boss battle, but a boat provides an inescapable closed off arena which can be a good place for story based puzzles. I.E. Someone on the boat is the necromancer, find out who, or someone on the boat has the thing that you need to steal, or anything like that.
Long story short, boats in D&D are the shit and here are a couple of boat maps I collected.
