The wrecked subs in Aberlady Bay are both XT-craft midget subs, training versions of the X-craft midget subs.
The Royal Navy built about 20 X-craft, and it was these subs that attacked the German battleship Tirpitz in 1943, heavily damaging her.
Tirpitz was finally destroyed in 1944 as she lay at anchor in a Norwegian fjord . She was attacked by RAF Lancaster bombers in using bombs specially designed to penetrate the heavy armored decks of battleships.
