He was 15 feet underwater, spearfishing on his Hawaii vacation. Chasing a fish deeper into the shadows, he almost swam right into a jagged shape jutting out from the muck.

He looked again . . . and caught his breath.

It was the wing of a P47 Thunderbolt fighter plane, its tip ripped off by the crash.

That was five years ago. James Egan hasn't been the same since.

"I know of 3,600 World War II planes that have been abandoned all over the world," says the 29-year-old Alexandria entrepreneur, who now devotes all his time to finding, recovering and trying to sell antique planes through his Warbird Salvors Inc. "I have 20 or so projects in the works right now."

There are, he says, only about 90 known, fully rehabilitated survivors of the 48,725 U.S. warplanes produced between 1939 and 1946, and only a handful of those can fly.

Unlike Bruce Hoy, a widely known New Guinea aviation curator, and others who go after lost planes as archeologists, or the U.S. Army's Central Identification Laboratory, which searches for bodies of military air victims, Egan is a pioneer in a new business, providing vintage planes for museums and rich collectors.

Believe it, the money is out there. Three years ago a rare 1943 Spitfire Mark 9 sold at auction for $390,000. Only 151 such Spitfires were then ld,10 sk,2 sw,-2 known to exist, and hardly any in flying condition.

It is distinctly a seller's market. There are today, Egan says, only four flyable P47s out of the 14,000-plus that were built, and maybe nine of the 15,000 P40s manufactured. And perhaps four airworthy B17 Flying Fortress bombers. And two Japanese Zeroes. And, of all the 34,000 ME109s built by Messerschmitt for the Nazis, just one left.

There are more stories than planes. A guy supposedly found a P40 buried in a field and dug it up and made a fortune. Six brand-new P38s -- the lovely twin-fuselage pursuit planes of the early '40s -- are reported to be waiting on an icecap in Greenland, where they belly-landed out of fuel. But which icecap? As many as two dozen B25 bombers may lie in the silt of Lake Murray in Columbia, S.C. At least 100 carrier planes are thought to be in Lake Michigan, ditched during carrier landing exercises.

Treasure hunting is going commercial in a big way, aided by new technology: side-scan sonar devices for charting sea bottoms, iron-detecting marine magnetometers, giant helicopters that can lift a bomber out of the sea or jungle.

Encouraged by Melvin Fisher and his golden galleon Atocha, not to mention the excitement over the Andrea Doria, the Titanic and the alleged Pinta, brokers have popped up to offer limited partnerships to steel-nerved investors, even though one leading backer has complained that "for every 50 deals I see, maybe one is worth further investigation."

This does not discourage Egan.

Several years ago he heard about a plane that someone had spotted in the jungle on Oahu (commercial pilots often send him post cards reporting finds; most can't be traced), and eventually, after elaborate research, he narrowed the site to four square miles. He flew to Hawaii, hired a helicopter and combed over the area, taking telephoto pictures.

At last, a flash of metal. He dropped the copter to treetop level above a tangled ravine. Suddenly the downwash scattered the vegetation and a great mat of leaves flipped over, revealing a silvery wing section.

"I took pictures," he says, "and when I developed them I saw these little black spots. I realized they were bullet holes. What I had was a P40B, an exceedingly rare model that everyone thought was completely out of existence."

Returning to the site with a couple of friends, Egan tried to bushwhack his way to the plane but couldn't get through. So he and a friend climbed into the chopper, took it down to 25 feet -- and simply jumped into the thick foliage.

The plane was in bad shape, but to Egan it was a bonanza. He found bullets, cockpit equipment, a belt buckle, the engine and a fairly complete airframe. No bones. He didn't look for bones.

"It was definitely shot down at Pearl Harbor," he says. "But the bullets were American. It was brought down accidentally by our own ground fire. The loss was reported in the official histories as a training accident, but to get way out there in that remote area with the amount of battle damage it has, the plane obviously was shot down."

From there on it was a matter of engineering. Egan hired a large copter to pull the wreck from the jungle in a net on the end of a 150-foot cable and landed it in a meadow four miles away. Now the plane is stored in crates, waiting for the day Egan finds the money to restore it, complete with bullet holes, and sell it.

He won't say where it is, either. He won't even tell you the airlines his spotters work for. There are pirates and claim jumpers in this rugged business, and secrecy is a daily fact of life.

"Money is always a problem. You don't get paid in advance. It's impossible to say what the value of a plane will be until you get it on a runway. Museums want them, but they can't pay much, so you look for a collector. Sometimes the collector will turn it over to a museum for the tax break. There are few connoisseurs, and fewer hunters."

Egan emphasizes that, while some competitors build replicas, he deals only in authentic planes. Not that he doesn't rebuild a lot. "As long as the frame is okay, you can build up the whole fuselage, if that's gone."

It's nothing for him to spend a year researching one job. Starting from a vague rumor, he has spent nearly three years tracking a B18 reconnaissance bomber that went down on a Hawaiian mountainside 10 months before Pearl Harbor.

He's surveyed the site, collected a 15-man team, arranged an exit route, wangled use of a Marine cargo plane and now only needs "a truly nominal sum of capital" to bring it out. Fourteen museums want the rare specimen, but probably the project will require some sort of corporate sponsorship.

"The B18 was a prewar sub chaser, and this one looks good -- it's not corroded at all. It could bring $100,000 -- or twice that."

In the course of his investigations he checked out The Honolulu Star-Bulletin of Feb. 26, 1941, which reported the crash. The six crew members survived with minor injuries, and Egan has actually located two of them. Francis R. Thompson, the copilot, has written him from Indiana:

"We were on a night training flight . . . flying east just off the north shore of Hawaii and just above a cloud layer when we developed a severe vibration in the right engine . . .We turned back west planning to land at a small airfield on the northeast tip of the island. In the process we got farther south than we thought we were so that at about 3200 feet altimeter reading we hit what we referred to as the side of a mountain."

The men lived in the plane for two nights, wrapped in parachute silk, awaiting rescue.

Thompson, a fresh lieutenant at the time, came out of the war a major and moved up to lieutenant colonel in the reserves. Wounded in the 1941 Japanese raid on Clark Field in the Philippines, he spent most of the war in Australia.

Today, an executive with an electric-motor manufacturer near Fort Wayne, Ind., he says he is surprised the B18 is still in such good shape. "I'd like to see it brought out," he says. "But they've been talking about this for five years."

"There are planes all over the place," Egan says. "I want to concentrate on mass graves because they're more profitable. I know of four locations where planes exist in quantity -- 20, 30, a hundred of them. It'll take maybe three years to develop a site like that fully so I can do all the planes in one visit."

Some are in mint condition (or were), still chained on the decks of sunken Liberty Ships. Some were buried during the war, still in their crates. Some were stored, so the story goes, on Pacific islands, nose to tail, scores of them, to be abandoned and forgotten.

(After V-J Day a legend spread about an island completely covered with brand-new jeeps, once destined for the invasion of Japan but later deemed too costly to remove. According to the legend, they were being sold by an Army-Navy store for $11, or was it $17, but somehow one could never find the store.)

What separates legend from fact is records. If there is indeed an islandful of abandoned bombers, there must be a record of it, languishing in an old-fashioned file cabinet in the back room of somebody's office.

It is those records that James Egan covets.

"I know where a couple of World War I submarines are. I've located some old Ford cars and Packards sunk on barges. I'm interested in sunken Liberty Ships along the East Coast -- some of their cargoes are quite valuable, and some are shallow enough to salvage."

But it's the planes that capture Egan's imagination. Though he was never in the service and never flew in a vintage warplane, he is fascinated by them, their beautiful complicated machinery, their role in history.

"I've got a Douglas Dauntless SBD dive bomber sitting in 600 feet of water off Hawaii. The SBD was the dive bomber that won the Battle of Midway, knocking off those carriers in a matter of minutes. There were over 30,000 produced, but now it's almost extinct. There are maybe three in existence. I'd love to get that one out."

Then there's the Heinkel 111 bomber in which Otto Skorzeny, the famous Axis war hero, tried to rescue Mussolini from the Allies, who had him interned at La Maddalena in northern Italy. The engine failed and Skorzeny ditched the plane. Egan says he knows where that one is, too.

Not to forget the plane that George Bush bailed out of near Japan, to be picked up in the ocean hours later. Egan won't even show you the locator map he has of the spot.

"It's joyful work," says Egan. "You talk to lots of people, you write to organizations and governments, and you spend your time scheming and planning. Right now I have to rent copters and crews, but someday I'll have my own. This business is about to take off."

Meanwhile, he watches his mail.

"I got a post card from Mexico saying there were three P40s in the jungle with their noses showing. I flew down there and sure enough, there were three planes. But not P40s. There's a lot of that. Still, I put them in my files. There's just so much stuff out there. I'd love to get hold of a P51 . . . some Grumman F4Fs chained to a deck . . . I may have a line on a MiG . . . a P47 . . . "