Fishman Island and Skypeia are stunning otherworldly environments, but probably impossible for regular folk to access.
Tottoland, Thriller Bark and the Boin Archipelago are also personal preferences, but obviously you can't simply stroll into such dangerous territory owned by pirates.
Sabaody Archipelago and "Future Land" Baldimore interest me, and you might actually be able to pay a ship to get you there.
The most beautiful but practical vacation destination is probably Water 7. It's a ship hub and also connected by the sea train. Judicial Island is close by, limiting how much pirate activity goes on there. And Iceberg is turning the island into a boat so it might start making world tours in the future.