1600-ton Royal Navy submarine, built 1918 as K19. 296ft x 24ft. Originally carried 12in gun (same as M1). In 1928 gun removed, replaced with hangar to carry folding-wing seaplane with catapult launch.

Position: 50 34.60N; 02 33.93W (all positions are GPS).

Depth: 30m.
Sunk: 26 January, 1932, while exercising off Portland, probably in attempt to surface and launch seaplane in record time. Its believed hangar door was opened while still under water. All 60 of crew lost. Eleven-month salvage operation, headed by Ernest Cox of Scapa Flow fame, failed to raise her.
Diving: Complete and upright. Jib of recovery crane sticks out forward of conning tower. Hangar door open, aircraft removed during salvage. All hatches sealed with steel and concrete, except for conning-tower outer hatch which is open, but inner hatch is sealed like all others. This is a war grave, dive accordingly.
Launch: Portland.