Excerpt from Shadow Divers by Robert Kurson, plus links to reviews, author biography & more

And they did it to explore. Many of the deep wrecks hadn't been seen since their victims last looked at them, and would remain lost while nature pawed at them until they simply didn't exist anymore. In a world where even the moon had been traveled, the floor of the Atlantic remained uncharted wilderness, its shipwrecks beacons for men compelled to look.

You had to have steel balls to do what Nagle did in his heyday. In the 1970s and 1980s, scuba equipment was still rudimentary, not much advanced past 1943, when Jacques Cousteau helped invent the system of tanks and regulators that allowed men to breathe underwater. Even at 130 feet, the recreational limit suggested by most scuba training organizations, a minor equipment failure could kill the most skilled practitioner. In searching for the most interesting wrecks, Nagle and the sport's other kings might descend to 200 feet or deeper, virtually begging the forces of nature to flick them into the afterlife, practically demanding their biology to abandon them. Men died--often--diving the shipwrecks that called to Nagle.

Even if Nagle's equipment and body could survive the deep Atlantic, he faced a smorgasbord of other perils, each capable of killing him à la carte. For starters, the sport was still new; there was no ancient wisdom to be passed from father to son, the kind of collective experience that routinely keeps today's divers alive. The sport's cautionary tales, those lifelines learned over beers with buddies and by reading magazines and attending classes, were beaten into Nagle underwater at antihuman depths. If Nagle found himself in some crazy, terrible circumstance--and there were countless of them on these deep wrecks--odds were that he would be the one who would tell the first tale. When he and his ilk survived, the magazines wrote articles about them.

Nagle pushed deeper. Diving below 200 feet, he began doing things scientists didn't fully understand, going places recreational divers had never been. When he penetrated a shipwreck at these depths, he was often among the first to see the vessel since it had gone down, the first to open the purser's safe since it had been closed, the first to look at these men since they had been lost at sea. But this also meant that Nagle was on his own. He had no maps drawn by earlier divers. Had someone visited these wrecks before, he might have told Nagle, "Don't brush against that outboard beam in the galley--the thing moved when I swam by, and the whole room might cave in and bury you if you do." Nagle had to discover all this by himself. It is one thing, wreck divers will tell you, to slither in near-total darkness through a shipwreck's twisted, broken mazes, each room a potential trap of swirling silt and collapsing structure. It is another to do so without knowing that someone did it before you and lived.

The Atlantic floor was still a wilderness in Nagle's prime, and it demanded of its explorers the same grit that the American West did of its pioneers. A single bad experience on a shipwreck could reroute all but the hardiest souls to more sensible pursuits. Early divers like Nagle had bad experiences every day. The sport eagerly shook out its dabblers and sightseers; those who remained seemed of a different species. They were physical in their world orientation and sudden in their appetites. They thought nothing of whipping out a sledgehammer and beating a porthole from the side of a ship, even as their heavy breath hastened nitrogen narcosis, the potentially deadly buildup of that otherwise benign gas in their brains. Underwater, rules of possession bent with the light; some divers cut prizes from the mesh goody bags of other divers, following the motto "He who floats it owns it." Fistfights-aboard boats and even underwater-often settled disputes. Artifacts recovered from wrecks were guarded like firstborn children, occasionally at knifepoint. In this way, early deep-wreck divers had a measure of pirate in their blood.

Excerpted from Shadow Divers by Robert Kurson Copyright© 2004 by Robert Kurson. Excerpted by permission of Random House, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.