Jim Slade had just arrived at the Los Angeles Airport after leading a river-rafting trip in Chile when he called his office to check in. He hardly had time to say hello before his boss asked, ''Do you want to go to Borneo?''
''I accepted the trip immediately - I didn't ask any questions until later,'' says Mr. Slade, who chalks up first descents of wild rivers like mountain climbers record first ascents of dangerous peaks.
Four months later, he was jetting his way with team leader Rick Ridgeway to join four other men at Pontianak, Borneo, starting point for the Great Borneo Traverse, the 1983 Camel Expedition.
The trip offered Mr. Slade, who is one of the foremost river guides in the world, the chance to add yet another first-river descent to his list - the Kayan River with its legendary Ampun rapids (roughly translated it means ''mercy, mercy''). Borneo natives also refer to this tortuous whitewater passage as the Embun rapids, meaning ''mist.''
To date, this genial, mustachioed adventurer has led nine first descents, including the Great Zambezi River in Africa from the bottom of Victoria Falls, a section of the Blue Nile in Ethiopia, and rivers in Turkey, New Guinea, India, Pakistan, and Argentina.
For the Borneo expedition, ''I was the only river-runner of the bunch,'' says Slade, whose team members - Ridgeway, John Long, Jim Bridwell, Peter Pilafian, and Stan Boor - are noted rock and mountain climbers.
The 43-day trip, which began July 22 and finished Sept. 3, spanned the breadth of Borneo. The team traveled all but 100 miles of the total 1,500 miles by water, setting out upstream on the Kapuas River from the village of Putussibau in native longboats. Later they endured an arduous trek through a stretch of unexplored highland jungle in the midsection of Borneo before confronting the rapids of the Kayan.
''When we did some research we found (the jungle area) was probably the largest unmapped area in the world; we didn't know what we were getting into,'' says Slade, who had visions of meeting ''the wild man of Borneo.'' Although he was assured that headhunting had stopped about 10 years ago, ''I just hoped everyone (in the jungle) had heard that,'' he says with a wry smile.
Although the team did meet some former headhunters, the biggest challenge turned out to be simply ''carrying on day after day'' through nagging heat, humidity, dampness, and insects. They were also challenged with precipitous trails, thorns, and slippery mud. ''It was slow going,'' Slade says. ''We were in the unmapped area for a full month.''
Despite the discomforts, he enjoyed the total immmersion into the jungle environment. ''The jungle has its own essence, it's lush and green - a riot of vegetation,'' he says, recalling the light filtering through the canopy of leaves overhead. ''It's certainly the most remote area I've ever been in.''
He also enjoyed meeting the members of four native tribes who accompanied the team as porters and guides during the crossing and gained a special admiration for the Punan Dayaks, considered to be the most primitive of the interior tribes. One of the chiefs, Daloon, personally led the party.
During the trek, the porters helped the team hack out places to sleep in the virgin jungle and built their own lean-tos, complete with raised floors, from leaves and branches, practically as fast as the Americans could pitch their tents.
''The Punan Dayaks,'' says Slade, ''are true masters of the bush.''
The natives also introduced them to delicacies such as wild boar and roasted lizard to supplement their more mundane diet of oatmeal, granola, peanut butter, fresh fish, and fruits.
Although the team only stayed more than one night in four places, it managed to catch glimpses of daily village life.
''The people still live a timeless existence'' Slade says. Many of the natives live in 500-foot-long houses divided into rooms housing extended families. Each long house has a veranda where women gather to pound rice and hang laundry.
At the government outpost of Longnawan on the edge of the unmapped jungle, two new team members, Frank Morgan and Peter Jennings, joined the group to replace members who could not continue. The newly formed team began the descent of the Kayan River in a 14-foot inflatable rubber raft.
They arrived at the Ampun rapids to discover the passage surpassed its reputation. Slade says the rapids were ''absolutely horrendous.'' The water rushed over boulders 25 feet high, plummeting into enormous potholes on the backside of the rocks.
''We portaged because it would have been a suicide run,'' he says bluntly. ''There was no question - no discussion whatsoever. It was disappointing, but it was also a relief.''
Even without the Ampun rapids, the Kayan River offered some white water which the team navigated safely before reaching Tarakan, its final destination, on the east coast of the island. ''The worst of it was a series of five rapids within three miles,'' says Slade, explaining that the normal procedure is to scout the rapid from shore before running it. ''The danger is, if you turn over you might not be able to get to shore before getting swept around the corner into the next rapid.''
Once, in Chile, Slade encountered the most dangerous situation in river rafting: hitting a stretch of rapids running through a gorge with vertical walls. This situation makes it impossible to scout the rapids, which might end in a waterfall, or to turn back or portage.
''There were two boats and mine went first,'' he says. ''Fortunately we managed to get through it.''
Mr. Slade, a would-be lawyer who graduated from Williams College in Massachusetts, got his first taste of river rafting in 1973 when a friend invited him to join the first descent of the Rio Grande de Santiago in Mexico. ''It was high adventure,'' he recalls. Since then, he has been chief river guide for Sobek Expeditions Inc., the largest international river-running company in the world. He spends little time at home in Oakland, Calif.
''A lot of it is just curiosity,'' he says, reflecting on his exotic experiences. ''It's not that I want to go everywhere, but there are still a lot of places I'd like to go.''