The lead characters are ex-astronaut Jeff Tracy, founder of International Rescue, and his five adult sons, who pilot the organisation's primary vehicles: the Thunderbird machines.
In "Danger at Ocean Deep", International Rescue must save the crew of a tanker when it sails into a patch of sea harbouring a fungus that reacts explosively with the vessel's cargo of liquid fuel.
The vessel is christened by Lady Penelope, who is attending the ceremony at International Rescue's request to rule out the possibility of sabotage campaign against the Ocean Pioneer fleet.
After Penelope contacts Tracy Island to report that all is well, International Rescue receives an emergency call from Hawaii, where a hurricane is making landfall and threatening a hospital on Oahu.
The puppet playing Lord Worden, the character presiding over the Ocean Pioneer II launch, previously appeared as Sir Jeremy Hodge in "The Perils of Penelope".
[3][4] Rating the episode four out of five, Starburst magazine's Tom Fox calls Brains' explanation of the radio interference "as amusing as it is improbable", adding that "it gets even better" when it is revealed that a dog food company has been dumping a fungus in the Mediterranean Sea.
He argues that by using these and other fictional substances as plot devices, Thunderbirds showed itself to be "surprisingly creative when it came to scientific accuracy", considering that the series was "seemingly aimed at the Look and Learn generation".
Coldwell also states that the opening sequence's "creepily atmospheric" scale model effects and "sinister" incidental music, combined with character dialogue, create an air of "dreadful inevitability" as Ocean Pioneer I sails into the fog.