The Torpedo fish is an electric ray capable of delivering a shock of up to 220 volts, which is used to stun or kill it's prey.
In the 1700's an American, David Bushnell, applied the name "Torpedo" to a weapon he invented. This first torpedo was simply a mine which was attached to the hull of a ship and exploded either by remote control or by a fuse. The name was also applied to floating mines and even blazing barrels of pitch carried into harbors by the tide.
Eventually, the name "Torpedo" became applied to a new class of weapons and the development of the mine continued on its own separate path. This new weapon was the Spar Torpedo Boat.
The Spar Torpedo consisted of a small boat having an explosive charge mounted at the end of a long pole projecting ahead of the boat. The boat approached an enemy ship under cover of darkness and placed the explosive charge against the ship's side and detonated it electrically.
In 1866, an Englishman named Robert Whitehead developed the first self-powered torpedo. It was described as blunt nosed "like a dolphin" with four long fins extending almost along the whole body length. The engine was driven by compressed air stored at 370 p.s.i. The original engine was based on two eccentric cylinders having a sliding vane to divide the volume into two parts. 
In this fashion the air pressure caused direct rotation of the outer cylinder which was coupled to a single propeller. The weapons carried wet gun-cotton warheads and achieved speeds of about seven knots to about 600 yards.
Over the years, the torpedo was gradually improved. First heaters were added to the cold-air engine for added boost. Later, electric motors, flywheels, gas turbines, and even rockets were used to provide thrust. Some torpedoes even use supercavitation to increase their speed to over 200 knots!
The Mark 48 torpedo at the cache location is powered by a Swashplate engine and contra-rotating propellers. It is capable of traveling at up to 71 knots, with a range of over 20 miles. In military applications it carries a 650 lb high explosive warhead, but in geocaching applications it only carries a keyholder and a logsheet.
geospyder and byjer will help with any needed maintenance of this cache.