Take control of a submarine trapped in the middle of a school of fish. A bunch of big, slow pufferfish drift aimlessly in the deep blue ocean, and the player needs to shoot them. Once you hit a pufferfish, it splits into several smaller fish that also need to be targeted. Keep going until all the fish and their little ones are taken out, and then the next wave will start.

Use the ARROW or WAD keys to maneuver the submarine. Press the SPACEBAR to launch a torpedo. To achieve high scores, target a large pufferfish first, then the medium-sized ones, and conclude with the small ones.

On touch screen devices, press the LEFT or RIGHT arrow keys to rotate. Press button A to fire torpedoes and button B to thrust forward in any direction.