Late one night (in the world of the future), a giant cargo hovership makes an emergency landing somewhere in the middle of the United States, and an enterprising citizen named Johnny Clinton stows away on it. In the space of only a few hours the craft crashes into the Pacific Ocean. The sole survivor is Johnny, whose life is saved by the "People of the Sea"--dolphins. A school of these fantastic creatures guides him to an island on Australia's Great Barrier Reef. There Johnny becomes involved with the work of a strange and fascinating research laboratory, learns skindiving and survives a typhoon--only to risk his life again, immediately afterwards, in a cliff-hanger of a climax!