C25 was built by Vickers, Barrow, and was commissioned on 28 May 1909.

C25 (Lieutenant. D C Bell) was machine-gunned and bombed by a squadron of five German Hansa-Brandenburg seaplanes based at Zeebrugge, off Harwich, on 6 July 1918, after being caught on the surface. Several rounds killed the commanding officer, and three lookouts on the conning tower. One of the bodies blocked the conning towers hatch so she was unable to dive. The first Lieutenant, Sub-Lieut. Ronald M. Cobb, and two engine room artificers cut off the leg of one of the bodies with a hacksaw to free the hatch. Another two crew members died while trying to close the hatch. The holes in the pressure hull were plugged by clothes and luckily E51 was able to tow C25. The seaplanes, led by Oblt.d.R. Friedrich Christiansen, returned re-armed and ready to attack again, but they were driven off by the arrival of the destroyer, HMS LURCHER.  C25 was raised and sold for scrap on 5 December 1921