|Laid down:||27 February 1908|
|Launched:||10 March 1909|
|Commissioned:||28 May 1909|
|Fate:||Sold, 5 December 1921|
|Class & type:||C class submarine|
|Displacement:||290 long tons (295 t) surfaced
320 long tons (325 t) submerged
|Length:||143 ft 2 in (43.64 m)|
|Beam:||13 ft 6 in (4.11 m)|
|Propulsion:||600 hp (450 kW) Vickers petrol engine, 200 hp (150 kW) electric motor, 1 screw|
|Speed:||13 knots (24 km/h; 15 mph) surfaced
8 knots (15 km/h; 9.2 mph) submerged
|Range:||2,000 nmi (3,700 km) at 7 kn (13 km/h; 8.1 mph) surfaced
55 nmi (102 km) at 5 kn (9.3 km/h; 5.8 mph) submerged
|Armament:||2 × 18 in (457 mm) torpedo tubes (2 torpedoes)|
HMS C25 was machine-gunned and bombed by a squadron of five German seaplanes off Harwich 15 miles (24 km) east of Orford Ness on 6 July 1918, after being caught on the surface. Several rounds killed the commanding officer, Lieut. David Courtenay Bell (Aged 23), 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, HMS E51 was able to tow C25. The seaplanes returned re-armed and ready to attack again, but they were driven off by the arrival of the Acheron-class destroyer, HMS Lurcher.
HMS C25 was sold on 5 December 1921.
- Hutchinson, Robert (2001). Jane's Submarines: War Beneath the Waves from 1776 to the Present Day. London: HarperCollins. ISBN 978-0-00-710558-8. OCLC 53783010.