I spent a good few hours the other day trying to remember this movie from my childhood. As far as I could remember, I watched it on TV around 1981 or so. I would have been 11 or 12 at the time. The movie at that time and it's concept intrigued me to no end. I was captivated by it.
The most I could remember about it was that there were some people that had been trapped inside a sunken ship at the bottom of the ocean for years. They had developed into a rather "cultist" society and even after being discovered by rescuers did not want anything to do with the real world on the surface. I remembered they shot one of the rescuers that surfaced inside the ship to explore it and then pretty much trapped any other rescuers there with them that entered their so called "world of utopia". Overall the movie was great back then. Subplots aside, I really enjoyed it so much, I am currently looking for a copy on VHS or DVD I can buy and own for myself and relive a little of my childhood memories thorough it.