This set of photos clearly show a model of UC5 in the swimming pool at RNTE Shotley.

UC-5 ran aground while on patrol 27 April 1916 and was scuttled. Her crew were captured by HMS Firedrake. The U-boat was salvaged and put into a floating dock by teams from Harwich and Chatham, led by Captain Young and Lt Paterson, a dangerous procedure because of the two mines still on board. Her captain had also rigged up explosive charges to wreck her in the event of abandoning, which the British press described as an attempt to kill the RN personnel who rescued his crew. Paterson was able to find and disable them after being warned by one of the prisoners. The U-Boat was towed first to Harwich, then on to Sheerness, where an approved party of journalists and even two war artists were taken to inspect it.
Later it was towed too and displayed to the London public at Temple Pier on the Thames and the following year in New York for propaganda purposes.

See a film about UC5 at https://www.youtube.com/watch?v=Y4XQQl6Q_7U&t=8s