This prequel to 20,000 Leagues Under The Sea takes place during the American Civil War and before Jules Verne's Captain Nemo embarked on a policy of aggression against warmaking sea power nations. The Nautilus is just doing scouting expeditions and comes across some survivors of a sea wreck and takes them to Nemo's undersea domain of Temple Meer.
Robert Ryan plays a dedicated and fanatical Nemo who has built an underwater Shangri-La which is surviving a whole lot of water pressure from the ocean. Among the survivors are a US Senator played by Chuck Connors, and British people Allan Cuthberson who has claustrophobia and doesn't deal well with the atmosphere, two brothers who are petty crooks, Bill Fraser and Kenneth Connor from the Carry On series and Nannette Newman and her young son Christopher Hartshorne.
As the High Lama of Shangri-La was, Ryan is looking for good people to help with his underwater paradise. He marks Connors as talent, but Connor who is on a mission from Abe Lincoln to European powers does not want to be the Robert Conway of Temple Meer. He's resolved to escape and all the men want out, each for their own reasons.
Among other things Temple Meer has is electric lights before Edison and alchemy. For water and electricity they have a machine which produces gold as a waste product. That really interests Fraser and Connor. In fact gold has no monetary value in Temple Meer. It's used for various drinking cups etc. because it is the most malleable of metals and doesn't corrode. Of course it's a got of value where Connor and Fraser hail from.
There are some nice underwater action sequences when the Nautilus tangles with a giant stingray all in the Jules Verne tradition. Captain Nemo And The Underwater City combines the best of both Verne and Hilton, two of the most popular authors around.
