Student raft regatta on the Charles - a waterborne demolition derby

It was not your typical day in Cambridge. The eateries and delicatessens in Harvard Square were not as congested as usual. And the Harvard University libraries seemed strangely dormant for this time of year.

The reason was simple. It was the first warm day of spring in Cambridge, and to help usher it in, the members of Adams House at Harvard were holding their 13 th Annual Adams House Raft Race - a tradition that draws more spectators than big-time crew races between Harvard and foes such as Cornell, Princeton, and other Ivy League heavyweights. Ten student ''crews'' were entered.

The race, viewed as a ''spring ritual'' by many students, was started 13 years ago by several enterprising Adams House members who wanted to do more than just play Frisbee and football along the river.

''This is the big one,'' explained Patty Miranda, a Currier House sophomore competing in her second race. ''We take this one seriously!'' Patty and her cohorts were out at 7 a.m. Saturday building their raft for the 12 noon start.

The rules were basic. All rafts must be home built, and can have no motors. The raft must stay afloat for the duration of the race. No raft may have a personal computer aboard, and propulsion may include paddles and the wind.

Also, no projectiles or other flying objects can be used between craft in the race (this last rule is like telling a baseball player that swinging a bat is illegal during a game). ''That was a big problem over the last three years,'' said Adams senior Paul Connelly, the race coordinator. ''We had people throwing eggs, water balloons, everything last year. Some people didn't even start. . . .''

As it came close to starting time, it appeared that this year, at least one raft would again have a hard time just getting to the starting line. The ''Yuri Andropov Medal'' for the fastest-sinking ship went to three Harvard freshmen whose small raft went under 45 minutes before the start.

Currier House, however, would not have that problem. Last year their seaworthy craft lasted the entire race - the only one that made it back to shore in one piece. With that result in mind, several members of the house decided to garage their craft over the winter. Their combination of empty oil drums, 4-by-4 beams, thick wire, and plywood - with a paddle wheel to boot - again proved to be an able vessel. But not the fastest.

But that didn't matter to most people.

''We're just out here to get wet,'' said one rafter, who startled the crowd with his appearance after emerging from the Charles. ''It's no fun to go down to the bridge and back without taking a spill in the goo,'' he said.

As the rafts began to mill around Weeks Bridge, the start and finish line, it became apparent to the multitude of students and other curiosity seekers that just who won the race was not important.

One ambitious student jumped 20 feet off the starting bridge to join his housemates for the race. ''That's the dedication that made this school great!'' shouted one supporter, pointing to the student as he splashed in the still-frigid river.

The race finally began almost an hour after scheduled, and the rafts, some, like Currier and Mather Houses', with well over 20 occupants, lumbered toward the Larz Anderson Bridge, where they would try to turn around and make it back to the finish line.

Students along the shore moved downriver, shouting support and throwing strange objects at the 10 craft. No one paid any attention to who was leading - as the first to finish is often looked upon as the chicken who avoided the fun. Instead, the crowds were hoping for a show of sabotage, which to some degree is what they got as rafts tried to sink one another while they moved slowly down the river. The Metropolitan Police Department's boat just drifted in and out of the congested race, the officer obviously amused.

Mather House finished first and was promptly disqualified from the race - for finishing first.

Mather House, however, had a better fate than Winthrop House, which was awarded the ''Reubin Askew Prize'' for the raft that never got into the race.

When it was all over, the crews clambored ashore - tired, bedraggled, but happy.

''Not a bad race from the house that FDR built,'' mused one race official, noting the famous former house member. ''(President) Roosevelt would have been proud!''