In Attack of the Alligators!, Thunderbird 4 is called into action when Culp intends to make a getaway with the phial of Theramine, threatening to pour in into the swamp unless he is given clear passage.
Gordon stands by in Thunderbird 4, diving into the river as Culp sets off in a launch. Suddenly, Gordon spots a fourth giant alligator. It attacks Culp's boat, and he is thrown into the swamp the phial of Theramine sinks to the river bed. Gordon goes in search of the phial but in the murky swamp its like looking for a needle in a haystack.
Gordon switches on Thunderbird 4's powerful searchlights and soon something bright catches his eye. Putting on his wet-suit he leaves the craft to takes a closer look, and to everyone's relief he finds the phial undamaged.