On 1st June 1939, the submarine HMS Thetis sank during trials in Red Wharf Bay, Anglesey, with the loss of 99 men.

After the tragedy, she was salvaged and recommissioned as HMS Thunderbolt serving in the Atlantic and Mediterranean theatres until she was lost with all hands on 14 March 1943, making her one of the few military vessels that have been lost twice with her crew in their service history