Sharks, Dolphins and Octopi are all natural enemies but must share the sea together. One player represents the Shark, the second the Dolphin, the third the Octopus. The board starts off empty. The Shark begins and places one of their pieces on any space on the board except for the center square, marked with a shell. Players then take turns, dropping their pieces on any empty space, including the center. A player's pieces may not be put next to any other players, i.e. they may not be placed in adjacent squares that share the same edge. Diagonally adjacent is fine.

The first player who can not make a move on their turn wins.