This film is a very good entry in the late ’50s sci-fi cycle, about a group of explorers and scientists who discover a lost tropical world below sea level in Antarctica (!) Reynolds (the pilot), Mahoney (the scientist), Smith, and Harvey crash-land and encounter dinosaurs and a survivor from an earlier expedition (Brandon). Great (although obviously indoor) sets, literate script, and good acting are the pluses. The dinosaurs are pretty shaky, especially the Tyrannosaurus (a guy walking around inside a dinosaur suit).
Mahoney seems a little miscast, but Brandon steals the show as the loner…his acting actually conveys the feeling that he’s been stuck here alone for years. This is a very good B+/A- sci-fi film that should better known than it is.