Karkat is a crabbing boat like on Deadliest Catch.

Aradia is a sailboat.

Tavros is a wooden dinghy, riddled with leaks.

Sollux is a biplane or whatever those planes with floaty boat landing gear things are.

Kanaya is a yacht, shiny and brand-new and incredibly luxurious inside.

Nepeta is a speedboat with a motor that breaks down a lot. Equius tows her back to the pier whenever she breaks down.

Vriska is a wooden pirate galleon boat thing.

Terezi is a jet ski.

Equius is an old tugboat, rusted and somewhat barnacle-encrusted but with a large and powerful engine.

Gamzee is a bright orange inflatable liferaft.

Eridan is an old German U-Boat.

Feferi is a high-tech submarine thing used for science.