Trying to Develop Some Magic Items for a Campaign on the Elemental Plane of Water

[Brenthar Gildenstone]

I've decided to run a campaign on the Elemental Plane of Water, and I was trying to figure out some new magic items to use... they don't have to be water themed, but there is a dearth of magical firearms, cannons, and persuasion-related items, as well as things related to piracy, swashbuckling, the searching for treasure, and various other things on the high seas...

I'm kind of running short on ideas, with this one... anyone got any advice or items that might work?