'Secret of the Giant Oyster' by Alan Fennell

When two amateur divers attempt to recover a giant oyster from restricted waters, they are apprehended by the crew of Stingray. However, the divers subsequently manage to persuade Commander Shore to order Troy and Phones to help them obtain the oyster’s priceless pearl. Meanwhile, Marina knows of the giant oysters, and is concerned about the legend of bad luck that surrounds them. Her fears are soon realised when Troy finds himself in danger…

Don Mason (Captain Troy Tempest), Robert Easton (Lieutenant George Lee ‘Phones’ Sheridan / Agent X20), Lois Maxwell (Lieutenant Atlanta Shore), Ray Barrett (Commander Sam Shore / Lieutenant Fisher / Titan)

Directed by John Kelly
Produced by Gerry Anderson

TX (UK): 11th April 1965

Notes:
*Featuring Captain Troy Tempest, Lieutenant George Lee 'Phones' Sheridan, Commander Sam Shore, Lieutenant Atlanta Shore, Lieutenant Fisher and Marina