United States Navy submarines, surface ships, and aircraft launch torpedoes, missiles, and autonomous undersea vehicles as part of training exercises.

At various points in history, newly manufactured torpedoes were fired as a quality control measure and these, too, had to be recovered before issuing them to the fleet.

At the close of World War I, U.S. defense spending was reduced, further curtailing the development of torpedo systems.

For example, during March 1945 the rescue tug ATR-63 was detailed to retrieve exercise torpedoes off Pearl Harbor five times.

They are capable of extended operation away from port, sailing independently, and have capacity to retrieve many exercise weapons without having to return to base.

For example, the submarine-launched Mark 14 torpedo of World War II replaced its warhead with an exercise head filled with water.

At the end of the torpedo's run, compressed air would expel the water, lightening the weapon sufficiently to float.

Also aiding the retrievers was that early torpedoes were primarily used against surface ships, so they ran at a set, shallow depth.

Exercise torpedoes have typically been painted in bright colors, often international orange, to stand out in the water.

[9] Modern torpedoes have electric propulsion systems that leave no trail of bubbles for a retriever to follow.

Further complicating location is that torpedoes are more likely to be used against deep-diving submarines, rather than surface ships, so not only is their course less predictable, but also the depth at which they run.

[3] Today, finding spent torpedoes is aided by dye packets that vividly color the sea where they complete their run.

A variety of snares and slings that encircle the body of the weapon, and various nosepieces have been used to attach lines to the otherwise smooth object.

Their crews would snare a floating torpedo, tie a line to it, and tow it to a dock or ship where it could be craned out of the water.

In the absence of purpose-built torpedo retrievers, a wide variety of small boats performed similarly.

Disadvantages of these early vessels included their inability to operate in difficult sea conditions, to stay on station overnight, to navigate on their own, and to recover more than one torpedo per trip.

Torpedo retriever boats are but one of the ways spent exercise and test weapons have been recovered by the Navy.

[3][12] A descendant of these early methods, recovering munitions as deep as 20,000 feet (6,100 m), were a series of increasingly sophisticated cable-controlled robots called CURV.

[13] Beginning in the 1950s, the Navy experimented with training a variety of marine mammals to recover sunken torpedoes.

[15] The United States Air Force has also operated drone and missile retriever boats to support its own training and development requirements and continues to do so to the present day.

The Navy's rules regarding these non-commissioned vessels have varied over the decades, but for much of their history they were not entitled to an official name or even a pennant number painted on their bow.

The vessels described below are listed in order of their introduction to the fleet.The navy built a number of these small, wooden torpedo retrievers as early as 1924.

[22] This class of torpedo retrievers began as conversions from 63' aviation crash boats, designated auxiliary vessel - rescue (AVR) by the Navy.

[23][9] One of these vessels was converted into the base fishing boat, Big Wheel, at Naval Station Key West.

Harbor Boat Building Co. of San Pedro, California built a single 72' torpedo retriever[29] as did National Steel and Shipbuilding Company.

[41] They were a derivative of an oilfield services crew boat which Sewart sold to support offshore oil installations in the Gulf of Mexico.

In 2012 the Navy awarded a firm contract for three of these vessels, with an option for a fourth, to Modutech Marine Inc., of Tacoma, Washington.

Marine Group Boat Works built four vessels of this class at its Chula Vista, California shipyard.

Among the technical innovations in their design, is the ability to run on B100 biodiesel and the use of Seakeeper gyroscopic stabilization to allow them to operate in heavier seas.

A number of surplus torpedo retrievers have been given to the Sea Scouts and other public organizations, and some are still afloat today.