As they head to Sagreb, Yugoslavia, to start competition Wednesday in the week-long World University Games, Susan O'Brien of the University of North Carolina and Mike Lambert of the University of Maryland take along their own motivations for wanting to do well as members of the U.S. swimming team.

O'Brien, 21, of Bethesda and a teammate of Lambert's on the Curl Swim Club, has yet to eclipse the 100-meter backstroke time she swam in the 1984 outdoor nationals that beat 1984 Olympic silver medalist Betsy Mitchell.

"My goal is to beat those times and if I stay focused, I can," she said. "I've been swimming for a long time and when you improve by one hundreth of a second, that's good. If I do best times, it doesn't matter what place I get."

This is Lambert's first international competition, and he wants to make the most of it. "I only have a few more years in this sport so I have to go at it full steam," said Lambert, 19, also a backstroker. "I can't mess around."

To participate in the University Games, an athlete must be a full-time student or have graduated within the past year. U.S. Swimming, the sport's governing body, chose athletes who placed highly in both the NCAA and senior national championships.

Some athletes, including Mitchell, have chosen to prepare for the Pan Am and Pan Pacific teams and will not participate in Zagreb.

"There's really a mixed level of swimmers on this team," said team head coach Samuel Freas of Louisiana State. "Most all of them are world-ranked swimmers with very little international experience. International experience seems to be a rocketing thing that puts people over the top."

Past University Games have produced unlikely stars. Bruce Hayes swam the 200 freestyle as a fluke in the 1983 games and was the only U.S. swimmer to win an event that year. Then in the 1984 Olympics, Hayes caught and beat overwhelming favorite Michael Gross of West Germany for the gold medal in the event.

"This is a much better team than in '83," said Freas. "But it's in July this year, which interferes with the total training picture for most of them. I think they'll be competitive, I know the Russians, Czechs and East Germans will be more prepared than we are."

Said O'Brien, "A lot of people turned this trip down to go to the senior nationals. For me, I haven't been on that many international teams and there was no way I'd turn it down. I'm gaining experience."

All the U.S. teams are making connecting flights to Frankfurt out of Dulles and will be staying at the Renaissance Ramada throughout the weekend. The 52-member swim team left yesterday, when the men's gymnastics team and the men's and women's volleyball teams arrived. The rowing delegation came through today and the track and field, diving and tennis teams arrive Sunday.