Clam

Clams are enemies in Super Mario 64. They are large pink clams. They are found in Jolly Roger Bay and Dire, Dire Docks. They open when the player swims near them, and can contain items such as Koopa Shells and Red Coins. They do damage if the player is inside them as they close.

Random Objects
According to reports, certain copies randomize the objects contained inside of clams. They range from the usual Red Coin and Koopa Shell to things such as 1-Up Mushrooms, Caps, and other various power-ups and enemies.