Warlords of Atlantis (1978)

In the pursuit of the mythic lost city of Atlantis, the intrepid Professor Aitken, his intellectual son Charles, and the adventurous Greg Collinson find themselves ensnared in a web of treachery. Betrayed by the crew of their own vessel, lured by the glittering allure of Atlantean treasure, they face an underwater leviathan that results in their bell-shaped diving vessel's destruction. In the icy grasp of the deep sea, they are pulled into the enigmatic world of Atlantis, where they encounter an advanced alien race with chilling intentions. These extraterrestrial beings, having enslaved the shipwreck survivors, plan to establish a dystopian regime in the human world akin to a Nazi state. Their interest is piqued by Charles' formidable intellect, which they believe could be a valuable addition to their cause. However, the fate of the human world hangs in the balance, and it falls to Greg and the rest of the team to thwart their malevolent plans. Assisted by Delphine, a brave girl born into slavery, they must navigate their way out of a city teeming with ominous creatures. The depths of the ocean hold more than just the ruins of Atlantis; they hold a dire threat to humanity that our heroes must overcome.

Warlords of Atlantis is an adventure movie featuring Doug McClure.

Warlords of Atlantis is currently streaming for free (ad-supported) on Tubi TV.