Destroy all ships by shooting torpedoes, blow up barrels to get more torpedoes.
Tap the screen to launch a torpedo, launch multiple torpedoes. Dont let the ships swim behind the screen.
With each level, the difficulty will increase, new types of ships will appear. Every fifth level you will land with special ships - bosses, for defeating which you will receive one of the bonuses.
Destroy floating barrels to get various bonuses or increase the number of torpedoes that can be fired at the same time. Islands and mines will prevent you from hitting ships.