HMS E17 conning tower, Royal Navy Submarine Museum, Gosport, 2 September 2013. 58 E class boats were built by a variety of builders 1912 - 1916. They were the backbone of the RN's submarine fleet during the First World. War. E17 sank in 1916 after striking an uncharted sandbank off (neutral) Holland, where the crew were interned until the end of the war.