Submarines are a special type of watercraft that can operate underwater.

They are typically large vessels with a high number of crew. Nuclear submarines may have a crew of over 100.

Submarines are used by the military as part of navy forces, protecting aircraft carriers, performing reconnaissance and carrying out other tasks.

Submarines are also used in other areas such as marine research, undersea exploration and salvage missions.

Some submarines can remain submerged for months at a time.

Submarines typically feature a raised tower which holds radar equipment, the periscope and other systems.

Submarines use ballast tanks to hold water, allowing them to submerge when necessary.

Early submersibles were developed in the 1600s before the first known military submarine was built in 1775. Named the ‘Turtle’, it held one person and was controlled underwater independently, the first verified submarine capable of doing so.

Both sides of the American Civil War built and used submarines.

The first submarine not propelled by human power was the French vessel named ‘Plongeur’. Launched in 1863, it used compressed air for propulsion.

Developed in the 1800s, torpedoes became an important part of submarine warfare.

French writer Jules Verne published ‘20,000 Leagues under the Sea’ in 1870, a popular science fiction novel that boosted interest in submarine design.

Submarine development and use continued through World War I and II, with German U-boats particularly effective in blocking supply lines to the UK.

Launched in 1954, the first nuclear powered submarine was the USS Nautilus. Nuclear power allowed submarines to operate at high speeds while staying underwater longer than other forms of propulsion such as diesel-electric.

Both the United States and Soviet Union maintained significant submarine fleets during the cold war.

In August 2000, a Russian submarine named ‘Kursk’ sank in the Barents Sea after a series of explosions inside the vessel, killing all 118 crew.