When Bill Endicott began racing tiny slivers of fiberglass down the world's wildest rivers a dozen years ago, the United States had an international reputation in canoeing and kayaking that was somewhere below the water line. If the U.S. team didn't appear at world cup competitions, no one would have noticed.

Yesterday, Endicott, 36, sat high and dry in Great Falls Park above the Potomac, where some of the world's best white water racers were competing, and smiled at how sweet the time between has been.

"I'm walking in a dream right now," said Endicott, who is coach of a U.S. canoe and kayak team that is the best in the world. Last year at the world championships in Wales, Americans won 10 individual and five team medals.

"The East Germans used to have the dominant white water slalom team," said Jon Lugbill, a four-time world champion in men's single canoe competition. "We have it now."

Lugbill is 20 and from Fairfax County. He and his brother Ron are part of a nucleus of world champions who live in this area. Other gold medal-winning siblings are Stephen and Michael Garvis of Great Falls and David and Cathy Hearn from Garrett Park. They and a dozen other local paddlers have made this area the mecca for white water competitors in the United States.

"We have our own little village of paddlers," said Abbie Endicott, Bill's wife and den mother to the white water team. The Endicott house overlooks the Potomac near Glen Echo, where the team trains, and serves as headquarters and occasional crash pad. Yesterday, the Endicotts were frantically pulling together the first day of a two-day competition to qualify for the Pan American Cup team.

Yesterday's competition was devoted to team events, conducted through a 30-gate slalom course set up on the Potomac just below Great Falls. Individual competition in canoe and kayak events begins today at 10 a.m.

"This is the first time we've been all back together since Wales," said Endicott, who wondered what effect being the best might have on his team. "It's always easier to be an underdog."

Endicott has been coaching the U.S. team since 1977. That year American paddlers began to challenge European dominance in the sport in numbers. But Endicott gives credit for that performance to Jamie McEwan, who first sparked American interest in international white water competition.

In 1972, the first and last time a white water slalom event was included in the Olympics, McEwan won a bronze medal in two-man canoe competition. He did it on television, and a group of teen-agers in the Washington area was watching.

The Lugbills, Hearns and Garvis took to the water with a passion. With their parents' support, they began competing, first locally, then nationally and finally where the wildest water flowed--Europe.

Because they had little training and not much tradition, the Americans used unorthodox technique and experimented with boat design. In 1977 the Garvis brothers took a revolutionary-looking two-man canoe to a world championship. The Europeans laughed when they saw it, then begged to buy it when the brothers placed fourth despite their lack of experience and technique.

Four years later the Garvis brothers won the world championship in Wales.

They sloshed down the Potomac like champions yesterday, while their coach, Bill Endicott, watched from the shore.

Most of these people are too young to remember the lean years,'' said Endicott.