The Secret Aquarium

The Secret Aquarium is one of thirty secret levels in Super Mario 64 and Super Mario 64 DS, where Mario, or the character played (different characters in the DS version), must collect eight Red Coins to get a Power Star in a large, flooded room.

The entrance to the level is in the same room as the entrance to Jolly Roger Bay. If Mario faces away from the painting and looks at the other end of the room, he will find two holes in walls. The hole on Mario's right contains a 1-Up Mushroom, while the one on the left is the entrance to the level.

The level itself is fairly easy complete, as drowning is the only way for Mario to die while in this place. Also, the many Coins in the level will help prevent Mario's health/oxygen from depleting.

Star
There is only one level in this area. In it, the player must collect the eight Red Coins. There is a Red Coin at the bottom of each of the room's four corners, while the other four are floating around the center of coin rings.