The picture is moving in its simplicity: a snapshot of a father and son that in another time, in happier circumstances, might have been lost in the stacks of photos that chronicle one family's life.

But to Hugh Cherry, it is a cherished reminder of the past, and of a son who laughed and cried and left an indelible mark of happiness and hope on all who knew him.

Timothy Robert Cherry, standing on the beach with his father, a broad smile crossing his tanned face, is dead--and Hugh Cherry doesn't want to forget.

Timothy Cherry was 27 when he died on a flat stretch of state highway north of Mesa, Ariz., in July, 1989. It was 6:30 in the morning, the skies were clear, and he was doing what he loved--riding his beloved Cannondale 12-speed bicycle.

He seemed to be doing everything right: riding with the flow of traffic, far to the right side of the road. But the driver of the Tioga motor home apparently didn't see him in time, and when the right-front fender clipped the Cannondale, Timothy Cherry was thrown violently forward.

In the flat, emotionless language of the police report, to be precise, Timothy Cherry was "thrown approximately 106.2 feet to the right at a slight angle, and came to rest 20.4 feet from the east edge of the northbound lane."

Cherry, a Huntington Beach native and accomplished triathlete, died of massive head injuries.

He was not wearing a helmet.

And now Hugh Cherry, in remembering his son, is determined that everyone know that his son might be alive today if he had.

"Tim didn't have a helmet on when he died, and if he had he may have been left a vegetable--we just don't know," said Cherry, a retired broadcaster who lives in Seal Beach. "What I do know is that wearing a helmet improves your chances.

"I think he was anticipating there not being much traffic that early in the morning. He exercised the same kind of carelessness that we all exercise on occasion. I would be the last one to blame Timothy for that accident. But I think if he hadn't been out on the road, it wouldn't have happened. And he should have been wearing a helmet."

Hugh Cherry remembers his son as a classic triathlete, lean and "all sinew and bone." He grew up in Huntington Beach, attended Arizona State University and settled in Fountain Hills, Ariz., working in landscaping.

It was four years ago that Timothy, worried about his father's health, persuaded him to take up bicycling.