Recreation of the shark in level 1-A of New Super Mario Bros. DS (despite this, the included ExGFX file is the Super Mario Land 2 shark). It swims slowly until it sees Mario, at which point it speeds up. Does not actually require sprite buoyancy or water, and can work in the air.
By default, it takes five fireballs to kill, similar to a Chuck. It also can't be jumped on, but any other attack kills it instantly.
The included ExGFX file goes over the Dolphin's frames in GFX06.