The Champions S01E13 - Twelve Hours

The Champions are assigned to escort an Eastern European head of state, Dubrovnik, on his visit to Britain. During a dive in a Scottish loch, their submarine is sabotaged and Dubrovnik is injured. Richard and Sharron are forced to face down a mutiny within the crew, who want to surface and save their lives; the submarine cannot be allowed to surface if Dubrovnik is to survive the surgery, which Sharron has performed.