Poseidon 8

Poseidon 8 was a sub-aquatic community designed and constructed to farm from the sea bed. (VG: Shadows of the Vashta Nerada) It was built on the former site of London after 75 percent of the Earth's landmass was flooded in the 23rd century. (VG: TARDIS) The wreck of the USS Eldridge was unintentionally placed nearby. (VG: Shadows of the Vashta Nerada)

History
When a bright light appeared, the base came under attack from a non-terrestrial shark-like fish, a sickness caused by vortron radiation and the Vashta Nerada and was therefore placed on lock-down by the computer Jones. The Eleventh Doctor, however, was able to access the lobby of Sector A using the sonic screwdriver, and this also reactivated the power generator. Amongst the foods harvested by Poseidon 8 were sea pumpkins, sea sprouts, sticky mushrooms and brine oil. Some of these aided the Doctor in finding a cure for the sickness. Under the base were many access tunnels, which could be used if another sector comes inaccessable. After discovering the wreck of the USS Eldridge, which held a gateway through time and space, the Doctor eventually helped to return the Vashta Nerada and other threats to their regular time and place. (VG: Shadows of the Vashta Nerada)