Unfortunately, it doesn't seem to be available on DVD. It's not a great movie, but it is wonderfully cheesy. I don't know that I'd want to watch it again, but it would be nice to have in the library to show my friends who appreciate fine cheese.
It's the story of a young fisherman named Demetrios who one day rescues a woman who's been stranded on a drifting raft in the sea. We never do learn why she was on that raft, but never mind. The story takes place in ancient Greece before Plato, so when the women claims to be Princess Antillia from Atlantis, Demetrios has never heard of the place. At first, he doesn't believe her stories of a land beyond the Pillars of Hercules, but eventually she talks him into taking her home, so off they go. Along the way they meet Neptune (sort of) and a fish-shaped submarine that happens to be filled with Atlanteans. Once Antillia gets home, she's shocked to find her father no longer in control and his right-hand man Zaren calling all the shots.
Zaren, who wants Antillia for himself, has Demetrios imprisoned with all the other sailors who've ever been unfortunate enough to run across Atlantis. They all work in the crystal mines now, when they're not being transformed into animal men by Zaren's lead scientist. Zaren, meanwhile, is developing a giant laser that he wants to use to conquer the rest of the world.
There are some big problems with the movie. I won't go into detail on the cheesy effects because really they're part of the charm. The biggest problem is with Antillia and Demetrios who are thoroughly unconvincing as lovers.
Antillia is arrogant and abusive when Demetrios first rescues her. She sneers at his hospitality and says that she's untempted by the meal he prepares for her. Eventually she seems to warm up to him, until he refuses to take her beyond the Pillars into open sea. Then she threatens to cozy up to some other guy in the village who she's sure will be happy to take her. Rather than telling her to take a hike though, Demetrios caves to the threat and says he'll risk his life to take her home on one condition. If they don't make it to Atlantis in a certain amount of time, Demetrios gets to turn back and Antillia has to marry him. In the business world, my friends, we call that a Lose-Lose.
Neptune is also disappointing for spoilery reasons that I won't go into, but beyond that, Atlantis: The Lost Continent is big, dumb fun. It's popcorn retro cinema. Sort of Planet of the Apes, but with fish-submarines, laser cannons, beast-men, and slaves chanting goofy-ass Atlantean work-songs. Also, segregated escape ships (because this was the '60s) and an arena fight to the death between Demetrios and some guy who's supposed to be menacing, but really looks like Dom Deluise. Also also, the Chief from Get Smart as the Atlantean High Priest. It doesn't get any better than that.
Three out of five minotaurs.