The potential for an enjoyable story existed, but the acting really holds it back! The premise involves four people trapped in a diving bell within a cave system. Cut off from those above, they have to figure out how to escape through the caverns—where they run into someone like their version of "Ben Gunn" (Maurice Bernard), who’s been down there for fourteen years already. Simultaneously, “Prof Wyman” (John Carradine) on the surface is working hard to devise a rescue plan, but with the diving bell missing, can he manage it? There's an abundance of rear-projection and papier-mâché used in the production. That’s not inherently problematic; however, the cavern settings and the very dull lighting contribute to a gloomy viewing experience. It feels low budget! The script and performers are equally unremarkable—no one leaves a lasting impression—and the characters fall into predictable patterns when danger arises. Whatever funds were available seem to have gone toward the coffee, because ultimately this isn’t particularly good, absorbing, or engaging, and you can easily recognize the (enlarged) old film clips from far away.

Source on TMDB