THEY WAIT THEIR turns in a special area.

Some sit quietly, alone. A few stretch muscles or pace nervously on the patch of artificial grass. Others chat boisterously with friends who came to watch, have jumped already or plan to go later.All steal glances at the oversize rubber bands to which they will entrust their lives. Will they prove thick enough when, suddenly, there is nothing below their feet but shallow water as their body plunges toward it?

This is bungee jumping, the sport of pumping adrenalin, pounding hearts and an unlikely blend of cold fear and wild exhilaration.

Cameras click and whir. Second thoughts skitter across a few faces when two candidates decide, after looking down from a steel cage suspended 140 feet in the air by a crane, that bungee jumping is not a good idea after all. They forfeit their $69 ($55 U.S.) fees.

Black clouds roll in. A rainstorm suspends operations as gusty winds buffet the cage, making it sway. Nerves tense and minutes drag by. Then the skies in Sydney, Australia, begin to clear and, below, the yacht pennants droop.

Jumpers are weighed to determine which of several cords will be used to stop their fall 6 to 8 feet above water.

Ankles are strapped snugly into heavy fabric-and-Velcro bracelets that are attached to each other, with a loop for the long cord. The other end is hooked to the bottom of the cage.

What bravado there was seems to continue until the jumper is put into the cage with two crew members, secured with a seat belt, and the crane begins lifting the cage.

On the way up, the jumper is coached in what to do on the way down, how to overcome fear and get the most from the jump. The spiel also seems designed to give the mind a focus and keep terror away.

"If you look down and start to get scared, look at the horizon," one crew member suggests. "Put your toes on the edge of the cage, then on our signal, jump."

Sounds simple, but a glance at the water below dries the mouth and churns the stomach. The height looks great enough from the ground, but the concept of 140 feet changes drastically with the new perspective.

In parachuting, the ground is so far down as to seem unreal. Here, it's easy to pick out details. The people look like ants; the yachts moored nearby are unfriendly shoals.

A crewman unstraps the seat belt and opens the gate. The cage moves in the breeze. Before there's too much time to think, and freeze, there's a count of "Three . . . two . . . one . . . BUNGEEEEEEEE!!"

Suddenly, there is nothing below but shallow water and the body hurtles downward. The adrenalin that had started the heart pounding now pours in.

The queasy stomach seems to be left up there, somewhere, and the weightless sense of free fall sets in just before the cord stretches, stretches . . . and then ends the dive.

It contracts again, then relaxes, contracts, like a rubber band, and the jumper gets a feel for manipulating the bounces, like a yo-yo or someone on a reverse trampoline.

By the time the cage, and the jumper, are lowered to the ground, the initial fear has been replaced by disappointment that it is over. A crew member grabs dangling hands and leads the body to a soft landing on a padded platform.

Some of the spectators applaud as the anklets are removed. The jumper stands, a bit unsteadily, and turns his attention to sorting out the sequence and feelings of the last few moments.

Another jumper is strapped into the cage.

The roots of bungee jumping are in Pentecost Island, part of the Vanuatu chain in the South Pacific. Every May, when the yams are ready to be harvested, young males go through a manhood ritual by jumping from a homemade tower with vines attached to their ankles.

The lowest platform is 30 feet and the highest more than 120. As men gain stature in the village, they move up to higher platforms.

Inauguration of the high-tech version is credited to the Dangerous Sports Club of Oxford University in Britain. Members dressed in tuxedos, among them Graham Chapman of Monty Python, made several jumps from bridges about a decade ago, including San Francisco's Golden Gate.

In 1987, New Zealander A.J. Hackett made headlines when he and a friend hid on the Eiffel Tower overnight and plunged through the open center from the second level, a height of about 360 feet.

Hackett brought bungee jumping back to New Zealand and commercialized it. Thousands of people take the plunge there each year and, in January at Auckland, the Commonwealth Games featured a demonstration.

A few of the comparatively rich and famous have given it a try, including boxer Jeff Harding, rugby star Wally Lewis and singer Deborah Harry, who went topless.

John Fahey, industrial relations minister of New South Wales state, delayed the Sydney operation for three months because of health concerns, then gave the go-ahead to what he called "glue-sniffing for yuppies."

But on Sept. 12, former Miss Australia Natalie McCurry and a companion were injured when one of the cords attached to their feet broke free as the couple made a joint 130-foot jump, leaving them dangling with their heads just above water.

In response, Fahey banned the sport in his state until a report was completed on the accident, which left McCurry with a broken collarbone. She and Andy Gulby, a staff member of the Bungee Bats thrill-seeking group, also were treated for neck and back injuries.

One fatality and a serious injury have been recorded in New Zealand. France, where there were three deaths in 1989, recently introduced regulations.