The Phantom Empire (1989)

When a man-eating cave creature appears with a fortune in uncut diamonds around his neck, Dr. Chambers' daughter Denae hires adventurers C & C Salvage to find the underground source of the gems. Accompanied by archeaological intern Andrew Paris, mineralogist Prof. Strock, and C&C's scruffy owners Cort Eastman and Eddy Colchilde, Denea's hopes of emerging from her famous father's shadow become as remote as getting out of the caves alive!