Scientist Doctor Wyman (John Carradine) invents a deep-sea diving bell, and experts Craig Randall (Robert Clarke), Paul Whitmore (Allen Windsor) and Laura Talbott (Sheila Noonan) descend to the depths accompanied by reporter Dale Marshall (Phyllis Coates).
They run into trouble when the cable on the diving bell snaps but manage to extricate themselves and seek shelter in a network of mysterious underwater caverns.
A heavily-bearded hermit (Maurice Bernard) appears and casts a lascivious eye on the girls (who spend most of their time bickering). He is a shipwreck survivor named Ingol, who tells the group he has been there for 14 years and there is no way out.
During the foursome’s incarceration, Dr Wyman seeks help from fellow scientists, and eventually, the explorers are returned to safety.
A convenient volcanic eruption disposes of the old man and all loose ends.
There is really nothing special about the film, though the underwater photography is effective, and the borrowed newsreel shots of flood, storm and volcanic eruption are used well.
Dr Millard Wyman
Dr J.R. Matheny