NEW YORK (AP) _ Hours after TWA Flight 800 plummeted into the sea, a weary firefighter docked his boat and reflected on the search for bodies and wreckage. He wasn't optimistic.

``They're going to be out on the water for a long, long time,'' said Ralph Lettieri, who spent a futile five hours looking for survivors. ``There's just so much left to do out there.''

Ten days later, much is still left to do. Wreckage remains on the ocean floor in 100 feet of water, salvagers are expanding their search and victims' frustrated relatives are clamoring for quicker recovery of the bodies.

But if past crashes are any indication, the process of retrieving bodies, salvaging wreckage and isolating an exact cause is a painstaking one that could take weeks, months, even years.

``Everybody wants answers immediately. It doesn't always happen that way,'' said Russ Chiodo, the Beaver County, Pa., emergency director who oversaw recovery efforts when USAir Flight 427 crashed near Pittsburgh in September 1994.

``People grow more impatient with each crash,'' Chiodo said. ``I really feel for them, but you have to look at it like this: Everything's being done that can possibly be done.''

Initially, the focus is on searching for survivors. Beyond that, finding flight data recorders, recovering bodies and, of late, protecting salvagers from biohazards can all slow recovery.

A criminal investigation adds additional dimensions: protecting the chain of custody for evidence, supervising subcontracted salvagers to make sure they're following rules, and reconciling the procedures of various government agencies.

``It's not just a matter of going down there and making sure you get everything,'' said Christopher Ronay, who as chief of the FBI's explosives unit investigated 30 aircraft bombings before retiring in 1994.

``If it was a recovery operation straight and clear, the divers could do whatever they could to bring it up,'' he said. ``But not in this case.''

All 230 people aboard the Paris-bound TWA 747 were killed when it exploded over the Atlantic on July 17; the bodies of just over half have been recovered.

Flight 800 is a particularly difficult case: the explosion at 13,700 feet, the scattering of wreckage in water with 3-foot visibility, the possibility that private boaters tainted waterborne evidence while trying to help in the hours after the crash.

After ValuJet Flight 592 crashed in the Everglades on May 11, the National Transportation Safety Board and Dade County officials searched the swampland for 30 days before suspending recovery efforts. They had identified only 57 of 110 bodies.

The 1994 USAir crash outside Pittsburgh presented a new wrinkle: It marked the first time NTSB investigators used biohazard protections at a major accident scene. The Occupational Safety and Health Administration issued the guidelines out of fear that diseases, especially Hepatitis B, could be transmitted through victims' bodies and blood.

The protections can slow the pace. NTSB officials say overheating in biohazard suits is common, and any activity _ from having a drink to urinating _ requires an investigator to leave the area, be decontaminated, shed the suit and start from square one.

While reluctant to compare crashes, experts cite similarities between Flight 800's salvage operation and that of Air India Flight 182, which fell into the Atlantic Ocean on June 23, 1985, about 120 miles southwest of Ireland. It was history's deadliest airline bombing; all 329 people aboard died.

By that year's end, despite a 22-day salvage mission that enlisted sonar equipment now being used in East Moriches, only 5 percent of the jet had been retrieved from the mile-deep seabed. And it took investigators two years to pin 1988's Pan Am Flight 103 explosion over Lockerbie, Scotland, on Libyan intelligence agents.

``Lockerbie, in a sense, was easier. It was right there over land and everything fell to the ground,'' said Victor Le Vine, who teaches a course on terrorism at Washington University in St. Louis.

On one thing experts agree: No amount of prodding should push investigators to sacrifice precision for speed.

``It's bad enough doing it the way we had to do it,'' Chiodo said. ``But to go down in the water, I couldn't imagine facing that. And if the relatives are moaning and griping because it's not done in a hurry ... I'd have to say simmer down. Because the people out there are doing the best they can.''