Jacko

Jacko was a sailor who was shipwrecked near Atlantis around 1970.

Biography
Jacko and Sean were the only survivors of the crew of a merchant ship, which sank after hitting a mine left over from the Second World War. (PROSE: The Underwater Menace)

Jacko was captured and put to work in a mine, where he and Sean met Jamie McCrimmon and Ben Jackson when the last two were assigned to the mines. The four of them escaped and met with the Second Doctor to aid in his plans to defeat Professor Zaroff.

Jacko and Sean's job was to convince the fish people to go on strike, leaving the Atlanteans without any food. After the Doctor flooded the lower levels of Atlantis, Jacko and Sean fled to the surface, where they saw the Doctor's TARDIS dematerialise. (TV: The Underwater Menace)