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.

As a DM, I love when my players absolutely love or gravitate towards an NPC I made. So many times my players latch onto an NPC and it becomes their mascot. It also works really well as a tool for plot hooks or to give players engaging side quests to chase.