British E-class submarines had fuel capacities of 50 long tons (51 t) of diesel and ranges of 3,255 miles (5,238 km; 2,829 nmi) when travelling at 10 knots (19 km/h; 12 mph).

Early in the morning of 17 April, the submarine, having dived too deep and become caught in the vicious current, ran aground some ten miles (16 km) in near Kepez Point directly under the guns of Fort Dardanos.

[5] The stranding was soon noticed by aeroplanes of the Royal Naval Air Service (RNAS), and reported to the SS Hindu Kush, the Allied submarines' HQ and depot ship.

[4] Finally, on the night of 18 April, two 17-metre (56 ft) picket boats,[6] one from Triumph, the other from Majestic, both armed with two 14-inch (356 mm) diameter torpedoes mounted in dropping gear, went in.

Departing at 2200 hrs, the two vessels managed to navigate the narrow channel for seven miles (11 km) before being detected and illuminated by searchlights, attracting a hail of fire from both shores.

Miraculously both boats remained unscathed, and when one carelessly directed searchlight briefly illuminated the stricken submarine, Godwin seized his chance.

Blinded by the lights, his first shot missed, and seconds afterwards the Turkish gunners scored their only hit, blowing away part of the stern and mortally wounding one seaman.

Now doubly laden, Triumph's boat fled downstream unobserved, the Turkish gunners concentrating their fire on the drifting and abandoned wreck of her sister ship.