[1] When war was declared with Germany on 5 August 1914, E6 was based at Harwich, in the 8th Submarine Flotilla of the Home Fleets.

[4] On 28 August 1914, E6 was one of eight submarines that took part in a raid against the German Heligoland Bight patrol using surface ships.

[7] On 25 September 1914, E6 fouled a mine on her hydroplane guard when on patrol in the Heligoland Bight, but managed to free herself and escape.

[8] On 13 April 1915 E6, on patrol near Juist, spotted a German submarine, but was unable to get into position to deliver an attack.

On 4 September E6 spotted the airship L9 and opened fire, but no hits were scored and E6 was forced to dive by the approach of an aeroplane.

A trawler had been sunk by a mine in the same position shortly before, and a British torpedo boat signalled E6 to avoid the minefield, but E6 ignored the warning and was lost.