Leviathan is the guardian of the anchor connecting Blue Resort to Altair's base of operations, Black Fortress. He is a giant purple fish with an antenna on his head. His nickname is Sewer Savage. Bomberman fights him in Stage 4, in a sewer/river area with torches lined along the walls, and Bomberman is on a raft. Leviathan will try to crush Bomberman with his antenna, or else spray bubbles at him with his tail, or else cut pieces off the raft. When this happens, Bomberman's movements determine which logs get cut off; if he stays still on the end of the raft, all the other logs will be cut off. Leviathan will usually stay still, then go underwater, and then do some form of attack. To damage Leviathan, Bomberman must hit his head with a pumped bomb, though his angler antenna often gets in the way. He takes four hits from a pumped bomb. When he attacks with his antenna (which he will not do if his antenna is burned), he opens his mouth first, giving Bomberman an opportunity to throw a bomb into his mouth. A regular bomb does 1 damage this way, and a pumped bomb does 2 damage. Eventually, Bomberman killed Leviathan.
Burn his antenna
Burn his tail
Throw a bomb into his mouth when he tries to crush Bomberman with his antenna