Like all pre-H11 British H-class submarines, H5 had a displacement of 364LT at the surface and 434LT while submerged.[2] It had a total length of 150feet, a beam of 15feet, and a draught of 12feet. It contained a diesel engines providing a total power of and two electric motors each providing power.[3] The use of its electric motors made the submarine travel at 11kn. It would normally carry 16.4LT of fuel and had a maximum capacity of 18LT.[4]
The submarine had a maximum surface speed of 13kn and a submerged speed of 11kn. British H-class submarines had ranges of 1600nmi.[2] H5 was fitted with a Hotchkiss quick-firing gun (6-pounder) and four torpedo tubes. Its torpedo tubes were fitted to the bows and the submarine carried eight torpedoes.[2] She is a Holland 602 type submarine but was designed to meet Royal Navy specifications. Her complement was twenty-two crew members.[2]
On 14 July 1916 H5 spotted the leaving the Ems and torpedoed her. U-51 sank with the loss of 34 of her crew; four men survived.[5]
HMS H5 was sunk after being rammed by the British merchantman Rutherglen when mistaken for a German U-boat on 2 March 1918. All on board perished including a US Navy observer, Lieutenant Earle Wayne Freed Childs from the American submarine AL-2. He became the first US submariner to lose his life in the First World War. All on board are commemorated on Panel 29 at Royal Navy Submarine Museum. The wreck's site is designated as a controlled site under the Protection of Military Remains Act. In 2010, a plaque commemorating the 26 crew was dedicated on Armed Forces Day in Holyhead.[6]