Barbary Terror

The Barbary Terror, also called the White Terror, was a supernatural being which appeared to sailors at sea and took their souls. Captain Benjamin Briggs dismissed it as "ungodly superstition". When a Dalek came on board the Mary Celeste, the crew and passengers mistook it for the Terror and jumped overboard to get away from it. (TV: The Chase)

Behind the scenes
In the novelisation, the sailors instead mistake the Daleks for "the folk of the sea", since the "Barbary Terror" actually refers to which had been suppressed decades earlier.