User blog comment:DancePowderer/What Goes Down Somehow Gets Back Up/@comment-1327586-20101226001621

its stated it chapter 608 that the island has coating mechanics... this would imply that the ships are re-coated (more likely it just pulls it off the bubble around fishman island, like when it entered) and are then given another float bag to be slowly inflated. or maybe the army gives them lift with one of THEIR own sea-kings to the surface