Steve Lundquist lowered his own world record in the 100-meter breaststroke tonight as the United States swimmers christened the new Parque Naciones Unidas pool with a sweep of the four available gold medals.

The villain among the North Americans as far as the crowd was concerned, was Bruce Hayes, the mild-mannered UCLA junior who turned a maelstrom of noise into absolute silence by edging Venezuela's Alberto Mestre in the last few strokes of the 200-meter freestyle.

Mestre went out fast, closley followed by Rowdy Gaines, with Hayes farther back in third after the first 100 meters. When Gaines faded, the crowd's gold fever became obsessive, but suddenly Hayes began to chop the margin.

The crowd's frenzy ended with the posting of the order of finish. Hayes, 1:49.89, and Mestre, 1:50.36, were under the former Pan Am record.

"I thought coming off the last turn there was no way I could catch him," Hayes said. "At 175 meters I was on his shoulder and I thought maybe I had a chance. But it wasn't until the last 10 meters I thought I'd win. The main thing I'm happy about is I didn't choke. There was a lot of pressure on me, but I stayed calm and didn't panic. At the world championships last year, the first thing I did was hit the panic button."

The awards were presented, the Star-Spangled Banner was played for the fifth time--including Kelly McCormick's gold medal for the three-meter diving--and then a funny thing happened. The crowd spontaneously sang the Venezuelan anthem in honor of Mestre, a University of Florida student.

"When we got down, they started singing and at first I didn't know what it was," Hayes said. "Being in his pool and his country, and with all that cheering, I'm sure it made him go faster. I'm glad I was up to it. That's my fastest time ever in only my first year of the 200."

Lundquist's world record of 1:02.28, which lowered his own mark by .006 of a second, came as a surprise, since he swam a mediocore 1:05.97 in the morning qualifying.

"That was depressing to me this morning," said Lundquist, who has completed his eligiblity at Southern Methodist. "Some people were saying I took a bath, but it was more a drowning.

"I was cold, I had the jitters and I wasn't excited, because there were only two heats and I knew I could get into the final. But tonight I felt good, right from the warmup.

"John (Moffet) took it out and I didn't see him. I didn't want to see him. I wanted to go out a little slower than at the nationals and I used my head a little bit more, so I had something left. It worked, but don't tell me John didn't have a great race. I didn't have any idea he'd be in that range."

Moffit, a Stanford sophomore, was timed in 1:02.36 and only Lundquist has gone faster.

Tracy Caulkins and Polly Winde, a North Carolina sophomore from Ellicott City, Md., gave the U.S. its second one-two sweep of the night in the 400 individual medley.

Caulkins, who tired badly in the concluding freestyle leg, was timed in 4:51.82.

Carrie Steinseifer, 15, grabbed the fourth gold by winning the 100-meter freestyle in 56.92, with Canadiens Jane Kerr and Kathy Bald placing second and third ahead of Kathy Treible.

McCormick, whose mother Pat won the springboard titles in 1951 and 1955, rolled up 500.73 points to win the three-meter diving gold by 10 over teammate Wendy Wyland, who finished second for the 11th time this year.

The United States wound up the day leading the gold medal race with 29--16 more than at the start of the day. Cuba was second with 18. The United States also led the overall count, 52-44.