Nothing puts quite the same tingling fear in swimmers, surfers, and divers--especially in the quarter century since Peter Benchley's novel Jaws conquered the bestseller charts--as the thought that a shark might be plying its course somewhere in the murky deep below. Thomas Allen plays on that fear in the opening pages of Shadows in the Sea with a strangely entertaining compendium of shark attacks on humans over the centuries. (The humans get their licks in, however, in the pages that follow, in which Allen recounts the exploits of William Young, an Ahab who chased sharks around the world.) Allen goes on to describe the ways in which scientists have attempted to understand the ways of sharks and their selachian kin, the skates and rays; looks at the place of the shark in the world's folklore and cuisine; and examines the commercial shark-fishing industry. His useful book closes with a species-by-species account of the world's principal shark types, from the 6-inch dogfish to the 20-foot great blue shark. Allen does a fine job of giving his readers an idea of the many ways these frightening but fragile denizens of the sea live their lives--and he provides plenty of anecdotes to disturb a beachgoer's dreams. --Gregory McNamee