A science fiction television series set in an underwater research base on the Challenger seamount. The year is 2020, and 250 people live in the base, which is dedicated to the exploration of the seas and the protection of marine life. Captain Michael Murphy is the base's commander, while the oceanographer Dr. Paul Williams is the leader of the scientific research team. The recurring threats included attacks from hostile marine animals (such as sharks and giant squids), environmental disasters, and threats posed by shipping activities on supposedly protected areas.