The C-class boats of the 1907–08 and subsequent Naval Programmes were modified to improve their speed, both above and below the surface. The submarine had a length of 142feet overall, a beam of 13feet and a mean draft of 11feet. They displaced 290LT on the surface and 320LT submerged. The C-class submarines had a crew of two officers and fourteen ratings.[1]
For surface running, the boats were powered by a single 12-cylinder[2] 6000NaN0 Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a 300hp electric motor.[1] They could reach 13kn on the surface and underwater. On the surface, the C class had a range of 910nmi at .[3]
The boats were armed with two 18-inch (45 cm) torpedo tubes in the bow. They could carry a pair of reload torpedoes, but generally did not as they would have to remove an equal weight of fuel in compensation.[4]
HMS C33 was built by HM Dockyard Chatham. She was laid down on 29 March 1909 and was commissioned on 13 August 1910. C33 was involved in the U-boat trap tactic. The tactic was to use a decoy trawler to tow a submarine. When a U-boat was sighted, the tow line and communication line was slipped and the submarine would attack the U-boat. The tactic was partly successful, but it was abandoned after the loss of two C class submarines. In both cases, all the crew were lost.
C33 was one of the two C class submarines lost while employing this tactic. She was mined off Great Yarmouth while operating with the armed trawler Malta on 4 August 1915.