HMS K13, a 1916 British Royal Navy steam-propelled K class submarine
The K21 is used for first-time flyers and trial-lessons, the K13 is used as a trainer, and the Ka6 is used for solo pilots, as is the Astir (G-CGBJ) used for more experienced pilots.
A memorial to the disaster was erected in Carlingford, New South Wales, Australia, paid for by the widow of Charles Freestone, a leading telegraphist on K13 who survived the accident to later emigrate and prosper in Australia.