Isto é The Deep Range por Arthur C. Clarke, baseado em um história curta do mesmo nome .
Don Burley is a whale shepherd, keeping the herds safe from predators. He gets unwillingly pulled off that job and asked to train the mysterious Walt Franklin, a former spacer with some undisclosed past incident that left him subject to panic attacks. The men eventually come to enjoy a friendship based on mutual respect and shared adventures in the deep ranges of the world's oceans. So you get plenty of suspense, some tragedy, love stories, and another glimpse of a possible future. The underwater scenes were breathtaking, even for me who likes to stay on dry land.