The steam yacht Cala Mara was built for Mr. W.H. Johnson by Vickers at Barrow in 1898. Designed as screw schooner by St. C.J. Byrne, she was registered at 216 tons gross and measured 152½ feet in length with a 21 foot beam. Although there is no record of her activated during the Great War, she was hired by the Admiralty for use as a mine-sweeper in June 1941 and served until 1943 after which she was then laid up until the war ended before being returned to her owners.