Players control Neptune who is exploring the depths of the ocean in search of his daughters held captive by the sea snake. The game is split into two sections. The first section has the player guiding Neptune through a series of underwater caverns while destroying jellyfish. The player also must shrink down weeds that get in their way. The weeds grow back to their original size after a few seconds, so the player must swim past them in a limited amount of time.

The second section has the player shooting crabs while avoiding falling debris. By shooting crabs, the player can pick them up and take it to the structure nearby where the player will see the daughters trapped in an aquarium guarded by the snake. To set her free, the player is required to drop the crab onto the snake's tongue. If the player repeats this enough times, the daughter is set free and the game restarts with a higher difficulty level.