The famed (yet, fictional) S.S Poseidon - the once great cruise ship that was hit by a rogue wave, was capsized, and sunk. Recently discovered by Shinigami when aquatic hollows began to show up, there has been some effort to make the Poseidon an actual training grounds. They have succeeded, but the ship remained forever underwater.

Welcome to Poseidon - a low visiblity aquatic area. You will see your assortment of fish, turtles, and other deep sea aquatic life. The occaisonal current will come and go, however, it is rare inside the ship. Most of your fighting will take place withing the ball room, renovated with an operational chandelier and pillars supporting the roof. It is the only place where you can be able to stand on your two feet without swimming as there is no water within this one room.