UNDERWATER UNDERHANDEDNESS . . . A simple missing-persons case: Find Frederick Walther's beautiful young daughter, who disappeared after a love affair turned sour. Simple, that is, until Leslie Walther's lover turns up dead in a fishy place-the seal pool at the Woods Hole aquarium. Part-time fisherman-part-time private eye "Soc" Socarides finds the highly loathsome Tom Drake had a number of acquaintances, business rivals, ex-lovers, and an ex-wife-all with reason to want him dead. Soc's investigation turns up so many knotted threads he could make a fishnet: a long-lost German U-boat, a cutting-edge underwater vehicle, corporate espionage, a shady munitions dealer, and a CIA spook from Soc's distant past. Soc hopes the net will snare a murderer. But if he makes one wrong move, it could drag him down to a cold, wet, silent grave.