Simon, author of an earlier, coastal alarm (The Thin Edge, 1978), sounds another well-warranted SOS of impending marine catastrophe--that is also, regrettably, flawed. The cited mistakes and problems include: commercial overfishing; pollution from industrial effluents, community sewage disposals off-shore waste dumping, and oil spills; the global warming trend (brought about by atmospheric CO buildup) that's raising sea levels through ice-cap melting, and threatening to drown much of the present Atlantic coast. Altogether: a complex and desperately important message--but badly botched in this stagy, ill-coordinated telling. Scientific details--for example, the action of sunlight on floating crude oil--are glossed over with ludicrous imprecision. Technological changes in the fishing industry are hastily summed up with hardly a concrete detail (there is no mention of William Warner's minutely observed and thoughtful Distant Water, 1983), and muzzy metaphors (""the four horsemen which carry the banner of ocean dumping"") tend to do duty for rational analysis. Only in the treatment of the Law of the Sea Convention does Simon rise to an admirable confrontation of complexities. The LOS agreement, she sadly concludes, amounts to ground rules for an international minerals grab in the name of sharing a global heritage--but the Reagan administration's abrupt withdrawal from the Convention and unilateral announcement of a 200-mile ""exclusive economic zone"" off US shores represents an arrogant rejection of even this frail and embryonic legal framework. Otherwise, only the hefty bibliography has something (if not everything) to offer.