Allied submarines had tried to pass through the Narrows of the Dardanelles long before the main campaign began. HMS B11 had sunk the old Ottoman battleship Mesudiye on 13 December 1914: her captain, Lieutenant Norman Holbrook, was awarded the Victoria Cross and every member of the crew decorated. The French submarine Saphir managed to get past the mines in January 1915, but then ran aground and was lost
From late April 1915 submarines tried to pass through the Narrows in order to attack enemy supply ships in the Sea of Marmara. The French boats had too short a range to get to the Marmara, but tried to operate above the Narrows. However, the Bernouilli was unable to progress against the strong current and the Joule was lost with all mines after striking a mine on 1 May.
The more modern British E-class boats, which had a longer range than the French ones, had more success, but still faced a difficult task in attempting to reach the Sea of Marmara. One, E15, had already been lost. She ran aground on 15 April and was destroyed by a British boat expedition three days later in order to prevent her being captured.
They had to pass through minefields and steel-wire anti-submarine nets without any metal blades to cut through the nets or the mine cables. They also had to avoid shore batteries and patrol boats, and to get through a 10 fathom deep stratum of fresh water that often made it very hard to control a boat.
The first submarine to reach the Sea of Marmara was the Australian HMAS AE2, captained by Lieutenant Henry Stoker, followed by the British HMS E14. Lieutenant-Commander Edward Boyle, E14’s captain, took her past the forts at Chanak at dawn on 27 April. At noon she encountered a number of patrol boats and fired a torpedo at a torpedo boat. It hit, but she was forced to dive, so could not see if the Ottoman vessel had sunk.
E14 was hampered by the efforts of enemy patrols to find her and one of her periscopes had been damaged. On the afternoon of 29 April she attacked two troopships that were escorted by three destroyers. The calm sea meant that her periscope was very obvious, so she had to dive immediately after firing. An explosion was heard and half an hour later one transport was seen to be heading for the shore, emitting a great deal of yellow smoke.
That evening E14 met AE2, which had had no luck and had only one torpedo left. Three days later the Australian boat was caught by the Ottoman torpedo boat Sultanhisar and sunk after a two hour fight. However, all her crew survived as prisoners.
On 1 May Boyle decided to attack the enemy vessels that were harassing E14. She sank a small gunboat and fired two torpedoes at a larger one, but they missed. This made the Ottoman patrols more cautious, but they and shore look outs continued to restrict E14’s actions. Her presence had some impact, but she was unable to completely stop reinforcements crossing the Sea of Marmara.
Four days later E14 encountered a large transport that was escorted by a destroyer. A calm sea and a well handled escort made the attack difficult, but Boyle was able to fire a torpedo from 600 yards when the destroyer was on the other side of the transport. However, it failed to explode.
The next day E14 met another transport, but it spotted her in time to turn back towards Istanbul. She pursued several ships over the next few days, but allowed all that she caught to continue as they were all carrying refugees.
Early on 10 May E14 evaded a destroyer. In the evening she encountered two large transports, escorted by a destroyer. The torpedo did not run true, but the second hit the second transport, which was the Gul Djemal, formally the White Star liner Germania, carrying troops to Gallipoli. She disappeared into the darkness. A witness later claimed that she sank with all hands, but the German Official History states that she was damaged, but was towed back to the Golden Horn the next day.
E14 now had only one torpedo left, which turned out to be faulty. Boyle kept her in the Marmara for a while in the hope that her presence would impede enemy movements, but on 17 May he was ordered to return to base.
Boyle was awarded the Victoria Cross, E14’s other two officers the Distinguished Service Cross and all her petty officers and ratings the Distinguished Service Medal. Boyle’s citation, quoted on naval-history.net, stated that:
The KING (is) pleased to approve of the grant of the Victoria Cross to Lieutenant-Commander Edward Courtney Boyle, Royal Navy, for the conspicuous act of bravery specified below:
For most conspicuous bravery, in command of Submarine E.14, when he dived his vessel under the enemy minefields and entered the Sea of Marmora on the 27th April, 1915. In spite of great navigational difficulties from strong currents, of the continual neighbourhood of hostile patrols, and of the hourly danger of attack from the enemy, he continued to operate in the narrow waters of the Straits and succeeded in sinking two Turkish gunboats and one large military transport.
 J. S. Corbett, H. Newbolt, Naval Operations, 5 vols. (London: HMSO, 1938). vol. ii, p. 374.
 A. J. Marder, From the Dreadnought to Scapa Flow; the Royal Navy in the Fisher Era, 1904-1919, 5 vols. (London: Oxford University Press, 1961-70). vol. ii, p. 312.
 Corbett, Newbolt, Naval. vol. ii, pp. 374-75.
 Ibid. vol. iii, pp. 26-27.