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What Waits Below, also known as Secrets of the Phantom Caverns, is a 1984 British-American fantasy adventure film directed by Don Sharp, and starring Robert Powell, Timothy Bottoms and Lisa Blount. In it, a group of soldiers enter a cave to plant an electronic transmitter, but encounter humanoids who have evolved differently, and may be the last survivors of the lost Lemurian civilization. It was Sharp's final theatrical film. It was shot under the title Secrets of the Phantom Caverns, which it kept in the U.K. and some international markets, but premiered in the U.S. as What Waits Below.