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Steel Diver is an unusual stage. It is a sidecrolling stage, similarly to Mushroomy Kingdom from Brawl. Players fight on top of a small submarine which serves as the main platform. This submarine is mostly out of the water but will sometimes go underwater for a short time, taking the battle underwater. In addition, the submarine travels across the sea, throughout different locations, such as a jungle-like ocean, a volcanic-like ocean, a tidal tempest, a battlefield with lots of battleships and many more. Sometimes, the submarine will encounter other, larger battleships and will bombard it with torpedoes, or, the submarine itself will be destroyed by the battleship. Players can also fight on teh huge battleships encountered on the way. They are much larger than the submarine. The submarine will appear frequently and retake the battle on top of it. Players cannot die by falling offscreen downwards. The key for KO'ing in this stage is by falling offscreen sidewards or upwards. Moreover, players can also drown or get fired by a torpedo.