Continuity mistake: At the very end of the episode, where Captain Scarlet, Captain Blue and Lieutenant Green are about to enter the airlock, their recognition badges are gone. Once they are inside the XK3 rocket, the badges have returned.
Continuity mistake: When Colonel White is being lowered onto the submarine, you can see that the harness is around his chest with his arms outstretched, but as he comes down the last few feet, he is gripping the harness strap with his hands.