Turbo Sub is a first person shoot 'em up. The player is the pilot of the Turbo Sub, the most advanced war device, with both flying and diving capabilities. Earth is attacked by evil aliens so the player is the last hope of the human race. He has to destroy numerous waves of aliens, dodging quickly to avoid collisions and enemy shots. Gameplay is simple: D-Pad is used to move up/down left/right and any button is used to shoot. The speed is not controllable. The aerial phase looks like the classic Afterburner but in a first person view. The player can dive whenever he wants. Sometimes headquarters will order the player to dive and it means the player is near a gem pod were he can collect diamonds. Near gem pods there is always a supply depot where bonuses (powerful shots, tracking missiles...) can be bought with the collected diamonds. Underwater the player moves a bit slower, and there are obstacles to avoid (like sunken antic temple columns).

In the two player mode, the winner of a level is the one who has the higher score in this level.