Voyage to the Bottom of the Sea : Season 4

Seaview experiences a sudden power overload and blows up, killing all hands aboard. When Admiral Nelson (who was at the Nelson Institute at the time of the accident) hears of the destruction of the Seaview, he gets an impossible to refuse offer from Mr. Pem (who survived from A Time To Die): in exchange for the use of the sub's nuclear reactor, Pem will transport Nelson back in time to before the explosion which destroyed Seaview. Once back in time, Pem renergizes his time travel device and