I have been running a pirate campaign for quite awhile and some that I would add are:
- Be careful how evil you let the players get. Too much evil is difficult to run especially in civilized port cities.
- I have allowed my players to learn new tool or skill proficiencies using downtime on the boat, there's a lot of traveling and this helps give them incentive to use the boat more.
- Don't take away their boat more than once or twice during the campaign for narrative reasons, it gets old and they invest a lot of money and resources into it. If they mess up and lose or sink their boat, that's on them.
- Make sure there's enough quests that need a boat, otherwise they might revert to old habits of traveling across land.