Johnny Clinton's adventures begin when the ship he has stowed away on sinks. Miraculously, two dolphins guide him to an island in the Australian territory. Johnny becomes close friends with a scientist who is devoting his life to experimentation and study of the "people of the sea" (his title for the intelligent dolphins). Johnny learns the art of skin diving quickly, becomes an asset to the scientist, and begins to think, live, dream dolphins. Mr. Clarke records the scientific discoveries and difficulties in accurate detail (much of it is only fiction and way beyond actual scientific discovery to date). The excitement of experimentation is emphasized, and therefore the book should appeal to both young scientists and adventure-seekers, although the readers may wish for more dialogue, less narration. Mr. Clarke is the author of Indian Ocean Adventure (1961, p. 684, J-246) and many adult stories of the deep; he has investigated the mysterious underwater regions himself.