Bermuda Triangle

The Bermuda Triangle was, as its name suggests, a triangular shaped region, in the western part of the North Atlantic Ocean where a number of aircraft and surface vessels allegedly disappeared mysteriously.

History
Another account says that the creation of the Bermuda Triangle was apparently caused by the Seventh Doctor and the Sleeze Brothers causing the Monk's TARDIS to implode. (DWM: Follow That TARDIS!)

Around 1908, a number of disappearances plagued the US Navy and Airforce. (DWBIT: #11)

In 1918, an alien ship crash landed on the planet Earth where its Octopod pilot remained in the oceans of the Bermuda Triangle. Around that time, it attacked the USS Cyclops whose human crew believed it to be a giant squid. At the time, the Tenth Doctor and Heather McCrimmon had used the TARDIS to travel to that period where they discovered the true reason why the Cyclops had sunk. They managed to temporarily stop it by throwing manganese ore from the cargo bay on it. This disrupted the Octopod's magnetic field, forcing it back into the sea. The temporary distraction allowed them to escape and the Doctor revealed that he could not save the ship as it was part of history and thus its destruction would remain to mankind a mystery. (DWA: Cyclops)

Behind the scenes
According to non-narrative information in DWBIT 11, sometime in the 1490s, a Dalek ship (possibly from the Last Great Time War) crash landed on an island, creating the Bermuda Triangle. It was thought that the ship caused magnetic disturbance and navigation instrument failure in nearby aircraft and sea vessels. Stories of strange animals and dancing lights were also linked to the area. On the morning of 12 September 1958, Flight Commander Benjamin K. Hooper briefed a squadron of F4U Corsairs on the strange disappearances in the Triangle. The squadron reported a strange disturbance or ripple in the air. The Daleks rose up from the island where the rusting Dalek craft had crash-landed, opening fire on the squadron, tearing the planes apart. The sea became a military graveyard, full of the Daleks' victims. Hooper later recorded this in his personal journal, praying that these monsters stayed in the isolated stretch of ocean and none of his men would ever have to see them again.