Topside
From Tardis Wiki, the free Doctor Who reference
Topside was a code-name for the crew of the Drum underwater base that operated from above the surface.
A man from this crew was called by O'Donnell. He told her a submarine had been contacted by Morse code to help them escape, however the Twelfth Doctor figured out that the ghosts had done it and told him to cancel the submarine (TV: Under the Lake)
