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)

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 sank the RMS Lusitania. (BFA: The Sirens of Time)

In the 1970s, Captain John Hart sent out a submarine expedition led by Commander Ridgeway to search for the Sea Devils. They captured the sub 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 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 submarines to get to the Conscience of Marinus. (DW: The Keys of Marinus)

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