The bodies of all but two of 19 young victims in Tuesday's gruesome canyoning accident in the Swiss Alps have now been recovered, leaving families grieving from Australia to Africa and a nagging question troubling adventure-seekers the world around: What is this new sport and how could it have gone so wrong so fast?

The young thrill-seekers were in a group of 45 who signed on for a day of body-surfing, rock-hopping and rappelling down Saxeten Brook below the scenic mountain lake at Interlaken. The tourists, led by professional guides from a Swiss company called Adventure World, were overwhelmed by a flash flood after a 15-minute summer downpour.

So ferociously did the wall of water roar down the rocky canyon, authorities said helmets and rubber shoes were ripped from the victims' bodies and many had severe facial bruising and head injuries from banging into rocks and trees flushed down by the torrent.

"This accident shouldn't have happened," said local fire brigade chief Robert Seematter, who told the Swiss newspaper Blick that local authorities had given clear warning of the danger of afternoon storms.

"It's surprising to me that they knew about the storm and went anyway," said Heinz Roethenmund, a member of the Swiss national whitewater kayaking team who lives in Bethesda but grew up paddling creeks in the Alps. "We all grew up knowing if there's a storm, you don't go near the river. In Switzerland, there is no dirt in the mountains, only rock," he said. "Water goes straight into the creek and comes down."

Canyoning, said Roethenmund, "is not dangerous if you do it right." The new adventure sport involves descending steep mountain creek beds by body-surfing down rapids, sliding down small waterfalls, jumping from ledges into deep pools and rappelling or climbing down rock surfaces while wearing wet suits, helmets, life jackets and climbing harnesses.

The group led by the Swiss outfitters evidently had little or no experience in the mountains and whitewater, a circumstance Roethenmund considers a formula for trouble. "It's a lot of fun if everything goes well but when things go wrong first-timers don't know what to do," such as keeping feet up in rocky rapids, staying away from submerged trees and other basic trouble-avoidance techniques, he said.

His concerns were echoed by Jed Williamson, a mountain guide and former instructor at Outward Bound. "There are hundreds of fatalities a year in the Alps," said Williamson, "and all the victims are dressed just right. They have all the right stuff except for skill and experience."

Canyoning as it's done in Europe is "like back-country snowboarding," said Williamson. "You're jumping off a cliff with no idea what's below."

From all indications, the group in Switzerland was mostly beginners. Of the dead, 14 were tourists from Australia and the others were from New Zealand, Britain, South Africa and Switzerland. Three were guides.

Canyoneering, a tamer form of the budding sport, is growing in popularity in the western United States, said Nick Wilkes, who outfits visitors for trips down Zion Narrows in Zion National Park near Moab, Utah.

European-style canyoning "is very dynamic, with a lot of water and waterfalls," he said. "They take a lot more risks. There's a lot more jumping into pools, rappelling through waterfalls. It's very exposed, more of an extreme adventure."

American-style canyoneering, by contrast, is more about hiking than river-running, he said. Wilkes said canyoneers who make the 16-mile trek down Zion Narrows hike through a 1,000-foot-deep, 20-foot wide gorge and occasionally must cross flat, cold, standing water, but there are no rapids and there is no historical record of flash-flooding there.

In European canyoning, Wilkes said, "The place isn't enough for them. They prefer to approach it more actively and aggressively, which leads to more risk."

Lee Belknap, safety director for American Whitewater, a national paddling organization, said he has been canyoneering in Utah, where he climbed up and down sheer rock faces using ropes and swam across cold, flat water. He said the canyons were "quite magical. It's an experience you can't get anywhere else. The scenery is some of the most outstanding in the world. But you have to be careful. The risk [of flash floods] is obviously there. We tried to go early in the day to avoid afternoon thunderstorms."

Belknap said tourists who entrust their safety to outfitters for water sports or mountaineering are in "a different ballgame. Now it's a question of public trust. Most outfitters have stringent safety guidelines but there may be a very few who don't pay strict attention to safety."

How do you tell which is which?

"It's a good question," said Belknap. "I really don't have an answer."

One thing is certain: The 45 tourists who signed on for a day of canyoning down Saxeten Creek had no idea they would soon be fighting for their lives in a raging maelstrom, many unsuccessfully. Nor did their families. "I'm just lost, I'm in a void," Paul Smith of Adelaide, Australia, who lost his 19-year-old daughter Briana, told the Associated Press.

It's clear from the tragedy in the Alps that any reasonably fit person can find someone to take him on an extreme adventure, but is extreme adventure really for everyone?

"My advice to people who want adventure is start somewhere near the bottom," said Williamson, the ex-Outward Bound instructor, who is president of Sterling College in Vermont, where outdoor sports are a key part of the curriculum. "Develop your own skills and judgment so you don't have to rely on someone else's."