Diving Adventure

Hal seized Roger's arm and pulled him into a cave in the cliff. The landslide thundered down in front of the cave ... The rocks piled up until the opening was completelyclosed. Their place of refuge suddenly became a prison.Hal and Roger are staying at Undersea City, built on the sea bed in the waters of Australia's Great Barrier Reef, helping to find ways of producing more food from thesea. Man-eating sharks arejust some of the terrifying creatures they encounter. But who starts the underwater landslide that almost kills them? When they unexpectedly discover sunken treasure, Hal and Roger realise immediately who wants them out of the way.