While the vast majority of top American swimmers get up every morning for an hour or more of aquatic exercise, Clay Britt usually slumbers on in the warmth of his bed.

And Tami Paumier, who with Britt will be heading to the Pan American Games July 1-15 in San Juan, Puerto Rico, has reached international competition in just three years in a sport that has many 12-year veterans at the ancient age of 18.

Paumier and Britt qualified for the U.S. team last month at the AAU national championships in Monterey Park, Calif., Britt in the 100-yard backstroke and Paumier in the 100-yard breastroke.

And in qualifying for the U.S. team, Britt, 18, of Rockville, and Paumier, 15, of Columbia, Md., have sent up a signal there are other lanes to success in swimming other than three to four hours of training a day for years on end.

Britt is one of the few swimmers to weather the pressure of age-group swimming and make it to the top as a senior competitor. Nationally ranked as a 10-year-old, Britt maintained his rankings all through his age-group swimming while following a workout schedule that was light in comparison with many of the nation's top competitors.

"We work out every afternoon from 5:45 to 7:15 and have morning workouts twice a week," he said. "Sometimes I went in the morning and a lot of times I didn't."

The 6-foot-3, 195-pound Bullis Prep senior has been badgered by college recruiters all year. Britt is a college coach's dream: a swimmer with good size and natural speed.

Britt, who will attend the University of Texas, holds the national high school mark in the 100-yard backstroke at 51.2, but has a best time of 50.01 set in the AAU championship preliminaries. "I feel the strong points of my race are the first 50 yards, my start and my turns."

Britt said his endurance is improving and noted his first 50-yard split this year was slower than last year when he went 50.1 - meaning he covered the second half of the race faster.

While Britt has been competing for a decade, the 5-foot-8, 125-pound Paumier has been in action only three years. When she was 12, Paumier slipped while practicing gymnastics and broke her arm in four places. When the cast was removed 13 weeks later, her doctor recommended swimming as good exercise.

"It was supposed to be rehabilitative but it turned out to be just fun," said the sophomore at Wilde Lake High School.

"It seemed like I moved up through, the groups fast and after a year I qualified for the National Junior Olympics," she said.

Paumier made her first trip to the senior nationals in August, 1977, at Mission Viejo, Calif., where she bombed in both the 100 and 200-meter breaststroke. Paumier had entered national competition before she had developed swimming savvy.

She was disqualified again in national competition in Houston last summer in the 200-meter breaststroke. But she also finished sixth at 100 meters in 1:13.3.

Paumier finally was ready for the nationals at East Los Angeles College. Swimming a few heats before American record holder, Tracy Caulkins, Paumier put it a blistering 100 meters in 1:02.9.

Caulkins qualified first for the finals with Paumier second. In the finals, Paumier gave Caulkins her closest race of the meet, finishing in 1:02.6 while Caulkins added another American record with a 1:01.82.

Paumier had established herself as one of the nation's best swimmers in just a little more than three years.