HMS E18 was an E-class submarine of the Royal Navy, launched in 1915 and lost in the Baltic Sea in May 1916 while operating out of Reval. The exact circumstances surrounding the sinking remain a mystery. The wreck of the submarine was discovered in October 2009. Design Like all post-E8 British E-class submarines, E18 had a displacement of at the surface and while submerged. She had a total length of and a beam of . She was powered by two Vickers eight-cylinder two-stroke diesel engines and two electric motors. The submarine had a maximum surface speed of and a submerged speed of . British E-class submarines had fuel capacities of of diesel and ranges of when travelling at . E18 was capable of operating submerged for five hours when travelling at . As with most of the early E class boats, E18 was not fitted with a deck gun during construction but later had a 12-pounder QF gun mounted forward of the conning tower. She had five 18 inch (450 mm) torpedo tubes, two in the bow, one either side amidships, and one in the stern; a total of 10 torpedoes were carried. E-Class submarines had wireless systems with power ratings; in some submarines, these were later upgraded to systems by removing a midship torpedo tube. Their maximum design depth was although in service some reached depths of below . Some submarines contained Fessenden oscillator systems. Crew Her complement was three officers and 28 men. Service history 1915 E18 entered service in the UK in 1915, commanded by Lieutenant-Commander R.C. Halahan. She joined HMS Maidstone on 25 June 1915 and soon began North Sea patrols with the 8th Flotilla at Harwich. On her one and only patrol prior to leaving for the Baltic E18 departed Yarmouth with D7 and E13 on 9 July 1915. On 14 July 1915 when at the mouth of the Ems deep in enemy waters Halahan brought E18 to the surface as he preferred the sea to using the toilet arrangements on board. While in this awkward situation a Zeppelin appeared, E18 dived to the sea bed but was easily visible from the air. E18 was then straddled with 12 bombs which caused no damage other than some embarrassment to Halahan in being caught unawares. The fact E18 was surfaced wasn't passed on via Halahan's patrol report, he stated he was submerged at 20 ft, and