The fastest torpedoes use combustion engines. In this case, the performance is limited by depth due to the back-pressure the engine exhaust must work against. Tail section . This extreme after section contains the control surfaces and propeller. Sea Mines Mine warfare continues to be one of the most effective means to deny use of a particular area to the enemy's ships and submarines.
Mines can be inexpensive and therefore numerous.
Many mines can use all three in any combination. Magnetic influence mines sense the permanent magnetic field causes by the iron in the ship's hull. Magnetic influence sensing. The magnetic field of a ship can be controlled by periodically degaussing the ship. However, this is a time consuming process which involves wrapping the entire hull in large cables and applying a magnetic field for several hours.