Sea Dragon is an arcade style side scrolling shooter. The player pilots a submarine through treacherous underwater caves in an attempt to destroy a heavily guarded reactor. Mines, gun turrets, and a variety of enemies provide obstacles to this goal. The submarine is armed with missiles, torpedoes, and a 'Big Kill' weapon (this affects everything onscreen) to help the player in their mission. The air supply is limited, so when possible the player must surface to replenish their air supply.