Submarine

A submarine was a ship designed to operate underwater.

In 1492, the Fourth Doctor claimed that Leonardo da Vinci's submarine design wasn't practical. (DW: The Masque of Mandragora)

In the early 19th century, Sir Adrian Stapleford tried to develop a submarine for the Royal Navy. His assistant Sam and he nearly suffocated in it when Lord Trumpsworth sabotaged it. They were rescued by the Fourth Doctor, who convinced Adrian to discontinue work on the craft. (TVC: The Emperor's Spy)

The first British submarine was launched in 1901. (DW: Enlightenment)

During World War I, submarines called U-boats were used by Germany. One of these, the U-20, sank the RMS Lusitania on 7 May 1915, which precipitated the entry into the United States of America into the First World War. (BFA: The Sirens of Time)

Germany also utilised U-boats during World War II. One such U-boat which was patrolling the English Channel in 1943 was sent forward in time to 1964, where it threatened to torpedo the Isle of Wight ferry. Sir Toby Kinsella of the Intrusion Countermeasures Group ordered Group Captain Ian Gilmore and his squad to investigate and render assistance to the personnel of the nearby Lanchester Naval Base. (CM: State of Emergency)

In the 1970s, Captain John Hart sent out a submarine expedition led by Commander Ridgeway to search for the Sea Devils. The Sea Devils captured the submarine and its crew, but the Third Doctor helped free them. (DW: The Sea Devils)

Some time later, a group of Daleks based underneath Antarctica used a captured naval submarine to attack Sydney as part of their plan to use the city as a base from which to convert humans into slaves and conquer Earth. (TVA: *Sub Zero)

Some time later, the Master used time-displaced Scottish warriors to seize a nuclear submarine and threaten Britain with obliteration if he wasn't given the Doctor's TARDIS. (TVC: The Glen of Sleeping)

In 1993 on a parallel world, Silurians used Kronosaurs to harass the remaining human submarines. (NA: Blood Heat)

In 2006, Mickey Smith launched Harpoon missile UGM-84A from the submarine HMS Taurean at 10 Downing Street. (DW: World War Three)

Later that year, the Ninth Doctor, Rose Tyler and Jack Harkness investigated the decommissioned submarines at an abandoned Russian naval base. (NSA: The Deviant Strain)

In 2594, the SSSSSSS used a submarine to explore Tyler's Folly. (BNA: Down)

On Marinus, the Voord used one-man glass submarines to get to the Conscience of Marinus. One of these submarines fractured and the acid sea killed the Voord within. (DW: "The Sea of Death")

On Olleril, Luminus was based on a submarine called the Gargantuan. (NA: Tragedy Day)