The Secret Aquarium

The Secret Aquarium, also spelled Secret Aquarium, is a secret location in Peach's Castle featured in Super Mario 64 and its Nintendo DS remake, Super Mario 64 DS. It is a large, cube-shaped fish tank filled with water that within the cloudy skies.

The Secret Aquarium can be found in the room with the Jolly Roger Bay painting. Since the door to the room requires at least three Power Stars to unlock, The Secret Aquarium, by extension, also requires at least this many to become accessible. In the Jolly Roger Bay room, The Secret Aquarium is accessed from a hole in the wall to the right of the door.

In The Secret Aquarium, Mario must collect all eight Red Coins for a Power Star to appear at the bottom-center of the area. Here, it is not possible for Mario's air supply to be replenished, and collecting coins is the only way to prevent his Power Meter from running out. Half of the Red Coins are found in the center of the rings made of coins, found midway up the area, while the other half are found in each of the bottom corners.