During wartime, the mundane duties of crew training and testing of newly constructed vessels takes on renewed importance.
The following accidents occured during normal operations and did not involve enemy action:
| Submarine | Nationality | Date | Type of Accident |
| AE.1 | Australian | 14 September 1914 | Unknown |
| E-20 | British | 09 January 1916 | Explosion |
| E.4 & E.41 | British | 15 August 1916 | Collision |
| Gustave Zede | French | 01 September 1916 | Explosion |
| Dykkeren | Danish | 10 October 1916 | Collsion |
| No. 19 | Japan | 09 November 1916 | Gasoline Explosion |
| E.36 | British | 19 January 1917 | Collision with E.43 |
| K.13 | British | 29 January 1917 | Foundered |
| A.10 | British | 17 March 1917 | Flooded |
| C.16 | British | 16 April 1917 | Collision |
| A-7 (SS-8) | American | 24 July 1917 | Explosion & fire |
| K.1 | British | 18 November 1917 | Collision |
| L-10 (SS-50) | American | 24 January 1918 | Man Overboard |
| K.4, K.6, K.14, K.17 & K.22 | British | 31 January 1918 | Collisions |
| E.34 | British | 20 July 1918 | Unknown |
| C.12 | British | 18 October 1918 | Allision |
| E-1 (SS-24) | American | 29 October 1918 | Explosion & Fire |
| G.7 | British | 1 November 1918 | Unknown |
Continue to next section, The Intra-War Years
Return to Peacetime Submarine Accidents