Undersea City

 

 (wikipedia)

WARLORDS OF ATLANTIS-1978-A British exploring vessel sponsored by an English prof. Aitkin (Donald Bisset) and his son Charles (Peter Gilmore) and commanded by Capt. Daniels (Shane Rimmer) get more than they bargain for when they go exploring in a special diving belt designed by American Greg Collins (Doug McClure). When a gold statue is found, the crew decides to mutiny and strand Charles and Greg underwater. But before that can happen the ship is attacked by a giant octopus. The duo, Daniels and a few others are "rescued" by Atmir (Michael Gothard) and his troops. They are taken to "the fourth city" where many English speaking people reside. No sooner do they get there when Greg starts a fight after meeting Delphine (Lea Brodie). Later, after they are put in prison, Charles is introduced to Atsil (Cyd Charrisse), who shows him the real hidden Atlantis because she admires his intellect. She explains how her race came from another planet (Mars). Delphine's father Briggs (Robert Brown) explains that he and everyone else are from other missing ships (his was the Mary Celeste) and they are controlled because of an operation performed on them. King Atraxon (Daniel Massey) says "the ruling class must always survive" while everyone else battles giant lizard-like creatures. He wants to create a utopia on Earth using science and force. 

Not the greatest sfx but overall, it's good. Director Kevin Connor was an old hand at this kind of production having already made THE LAND THAT TIME FORGOT (1974), AT THE EARTH'S CORE (1976) and THE PEOPLE THAT TIME FORGOT (1977) (all three featuring McClure).

Thanks for reading!