U-96 "Neun Sechs", a type 93 submarine. Launched 15th of February 1917, commissioned almost a month later in April. She served and survived the first world war.

The following is a verbatim transcription of the recorded activities of SM U-96 known to British Naval Intelligence, Room 40 O.B.

"SM U-96. Kaptlt. Jess, from SM U-79, in September 1918 to SM U-90. Came off the stocks at Kiel early in 1917, joined the Kiel School and remained there until about the end of May, when she left for the North Sea, being attached to the 4th Flotilla.

29 May - 21 June 1917. To S.W. of Ireland, northabout both ways, with SM U-95 on the way North as far as Shetlands. Claimed 8,000 tons.
10–30 July 1917. To S.W. of Ireland northabout both ways. Claimed 7,600 tons. Reported periscope damaged by a collision.
24 September - 16 October 1917. Went through Channel and operated in western approaches and Irish Sea. Returned northabout and by Sound. Sank 9 vessels of which Lloyds Registered Tonnage was 34,881 tons. Submarine claimed 37,000 tons.
21 November - 9 December 1917. To Irish Sea by Channel both ways. Claimed 35,000 tons. While returning from this cruise U-96 rammed SM UC-69 off Barfleur, an officer and 10 men of UC-69 being drowned.
14–20 February 1918. Went north but returned with defects.
14 March - 8 April 1918. To Irish Sea. Northabout both ways. Back via Sound. Claimed 19,000 tons. Seems to have been used in attempt to cut off transports from England to north of France.
25 May - 22 June 1918. To Irish Sea and south of Ireland via Bight and northabout. Back northabout and Sound. Sank 2 S.S. and fired on fishing fleet. Attacked 2 U.S. destroyers unsuccessfully, also 4 S.S. Was depth-charged on 4 June in Irish Sea, and returned with various defects. (Possibly depth-charged by HMS Viola on 18 June in 61°49'N., 0°20'W.)
30 July - 23 August 1918. Went northabout, found North Channel unsafe and proceeded to St. George’s Channel. Sank 1 S.S. only, and returned with starboard engine out of order, and bearings of port engine damaged.
20 November 1918. Surrendered at Harwich."

cd_young said:
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VERY late reply, just stumbled across this.

This isn't a WWI sub,it's the Type VII-C from WWII.
https://en.wikipedia.org/wiki/German_submarine_U-96_%281940%29

This one: https://www.youtube.com/watch?v=R4GjYgJMENk / https://en.wikipedia.org/wiki/Das_Boot

Also, the swordfish on her hat was (WWII's) U-96's symbol:
http://media.gettyimages.com/photos/naval-warfare-uboat-war-u96-unter-the-command-of-ltcommander-leaving-picture-id542362263