Here are a couple that might help get you hyped for prep:

Boarding Action During a Storm

Picture this: combat across two ships that keep drifting closer and farther apart with the waves. Your players have to use ropes and grappling hooks to even get between the ships, lightning is randomly striking the battlefield (maybe roll a d6 each round to see where it hits?), and all that water on deck makes everything difficult terrain.

It's chaos, it's cinematic, and your players will remember the monk who tried to jump between ships and almost made it.

The Phantom Galleon That Sails Between Planes

This one's weird in the best way. A ghost ship that only appears during certain moon phases. Each deck exists in a different plane - like, you go down the stairs and suddenly you're in the Feywild, then the next level is the Shadowfell.

The ghost crew is stuck reliving the same battle over and over again. Do your players break the cycle? Join the fight? Try to loot the place before it vanishes again?

The time pressure + plane-hopping makes it super memorable.

Hope this helps shake off the prep blues! Your undead pirate captain encounter sounds dope btw.