"THE CO-ED swim will start in just a few minutes, as soon as we get the kayaks out of the pool," Mrs. Alice McCabe, the spry, attractive director of Radcliffe swimming, said. A student with neatly combed blond hair and a blond moustache paddled by. "The Harvard-Radcliffe Kayak Club didn't have a home," Mrs. McCabe explained, "so we welcomed them to ours."

In the Radcliffe Gym pool, where the kayakists were practicing, a girl named Jennifer was learning "to roll"--the technique by which a kayakist rights himself after tipping over. Jennifer, under the direction of a red-headed boy named Tom, tipped over at will, but had not yet mastered the difficult stroke for completing the roll. The clock above the pool showed 8 p.m., and Jennifer and Tom reluctantly pulled their kayak out of the water.

Three boys, who had been nervously waiting in the Men's locker room, joined the small group of people already at the pool. One of them, wearing a tight white bathing suit, promptly sat down on the edge of the pool and gazed romantically toward the deep end.

"The trick is to push hard with your upper arm," Tom, the treasurer of the Kayak Club, was enthusiastically telling his admirers. 'To roll a kayak, you have to make a wide sweep with your upper arm." Jennifer dove into the water with a resounding smack. "The water's great," she cried.

The second of the new boys pulled in his stomach, put his hands on his hips, and looked back and forth from the clock over the pool to Jennifer, who was swimming laps. When a slim girl in a pink bikini emerged from the Ladies' locker room and slipped quietly into the water, the boy in the white suit abandoned his romantic look and began a fast crawl down the middle of the pool. The third boy, unable to find a secure place for his watch and wallet, held them self-consciously in one hand and, taking off his glasses which were fogged up from the heat, joined two girls in a discussion of Chem 20.

"It's deceptively easy to roll," Tom said, fingering the rubber nose clips that hung around his neck. He watched Jennifer in the pool. "But the first time is always hard."

THE BOY with his hands on his hips suddenly dove into the pool, scrambled back out, wiped the water from his face with a grimace, and put his hands back on his hips. He was a freshman and his name was Ted. "I like to swim," he said, "but I was hoping there would be water polo. I just came for the hell of it.... I wish there were more girls."

A short while later, only the girl in the pink bikini and the boy in the white bathing suit were still in the water. After a minute he stopped and resumed his place on the edge of the pool. Moments afterward, the girl climbed out and sat next to him. They began to talk.

"What I like most about Harvard," Ted went on, "is that you meet so many radically different kinds of people." Ted, whose field is government, admitted that he would like to be President someday.

Tom and Jennifer, who were talking by the side of the pool, saw that no one was swimming and retrieved their kayaks. Jennifer got into one and Ted, who had joined them, got into the water. Tom hopped into the water, secured his nose clips in place, and started to help Jennifer with her roll. Ted paddled at the other end. "The trick is to move your arms like a corkscrew," Tom said, holding Jennifer at the wrist and elbow. "That will flip you over and up."

The girl in the pink bikini stood up and left to change. "I like these swims," the boy in white, who had sat next to her, remarked. "It's live entertainment, and you can meet people. I met a girl at one last year."

In the pool, Tom held Jennifer around the waist to steady her in a position midway between over and up. Jennifer, with one arm straight forward and the other straight back, was breathing hard from the exercise. The boy in white waited by the edge. Ted went on paddling in circles.

There was no sign of the girl in the pink bikini. The boy in white shrugged, "Well, I'll call her tomorrow," he said, and walked off. Jennifer tipped herself over, but couldn't complete the roll and had to push herself from the kayak. She came to the surface, coughing from the water she swallowed, and then burst out laughing with Tom.