Watch Voyage to the Bottom of the Sea Specials in Australia

The Seaview is an atomic submarine designed by Admiral Harriman Nelson. On its initial launch some politicians are visiting it to see if all the money they poured into it is worth it. It is while they are at sea that they learn that the belt of radiation covering the Earth is on fire. Nelson is asked to attend some kind of international conference to determine what to do. It is while on route that Nelson comes up with a plan which he presents at the conference. Nelson proposes that if an atomic missile is launched from the Seaview at a precise moment, it will cause it to blow up. Another scientist claims that the belt will burn itself out when it reaches a certain temperature. But Nelson says that if they wait for his proposal, they will miss the window of opportunity that he told them of. Nelson leaves, boards the Seaview, and heads off to make his rendezvous with radiation belt. However, Nelson's driven manner, causes friction between him and Captain Crane, whose relationship with him is more paternal. As they push on, some of the crew members don't want to follow the admiral, and if that wasn't enough, there appears to be saboteur on board.

Season 4 Volume 1 of the DVDs features a color version of this episode which whilst filmed in colour was only transmitted in b&w... A gigantic tidal wave will destroy much of the civilized world, but Admiral Harriman Nelson has a plan to stop it -- Seaview will set off a nuclear explosion at precisely the right time and place. Evil forces seek to destroy Nelson before he implements his plan -- in the chaos following the tidal wave, they hope to take over the world! Seaview's original Skipper is killed and it's Lee Crane from the US Navy to the rescue.