You found it, Sly! This is where Raleigh's gang of crabs stashes his sunken treasure.
― Bentley to Sly, as the latter enters the crabs' lair[src]
Sly hopped inside a submarine and dived down into an underwater room, where Raleigh's gang of crabs stashed his sunken treasure. Sly had to use the submarine to destroy forty treasure chests[note 1] in order to gain the treasure key, doing whatever it would take to prevent any crab from making off with any treasure.