I am a great fan of "old-fashioned" sci-fi, and Robert Silverberg is one of my top five favorites. He manages to put you into an alien environment or situation very convincingly, but keeps the human condition intact. This book takes place on a water world that is sparsley populated by humans, who have an uneasy relationship with the native species. They are alien to a degree that makes their behavior and motives a mystery to humans, with tragic and far-reaching consequences. This unknowable alien situation is one that Silverberg has used in the past (The Alien Years) and does VERY well.
Just re-read this one and was pretty engrossed. I've not been reading much sci-fi lately. There are lots of water-creatures described, a total fantasy world of water and artificial islands, a little violence and gore, a little sex, a little romance, a little religion/philosophy. Something for everyone. (Except the kids, a fair sprinkling of not-for-kid words.)
Not one of the Silverberg books I've enjoyed the most.