THE POST-SUNRISE boathouse traffic bustled one recent morning at Thompson's Boat Center, off Rock Creek Parkway near Georgetown. College rowing teams as well as more leisurely types were busy launching their boats into the Potomac or returning the fragile wood and fiberglass shells to their racks inside the boathouse. Dressed in shorts and T-shirts, the rowers stroked away from the dock, their rowing shells resembling jumbo-size water bugs.

Rowers are a dedicated bunch, up earlier than most people even begin to think about making coffee. Dawn is when the water is the calmest, the motorized boat traffic minimal. Given Washington's notoriously steamy summer months, mornings are also the coolest time.

Because of the sport's physical benefits -- like swimming and cross-country skiing, it exercises all the major muscle groups -- Washingtonians are taking to the water to learn one or both of the methods of rowing: sweep and sculling. In sweep, each rower handles one oar, and in sculling, the rower has two oars, one in each hand. Sweep is done in two-, four- or eight-person boats. Scullers use singles, doubles or quads.

Many people learn to row in school. The Washington area has more than 1,200 high school rowers, the majority from public high schools. Most of the colleges and universities located here field both men's and women's crew teams. Yet the fastest growing area is in club rowing. Capital Rowing Club, formed last June, already has over 300 members, according to club president Walt Steimel, and taught over 100 people to row last summer. The Potomac Boat Club, located next to the Key Bridge, has a two-year waiting list for membership.

The reasons for rowing are as varied as the rowers themselves. "Rowing takes the grace of a ballerina with the strength of a football player," says Maureen Fitzgerald, a 33-year-old soon-to-be mom and Potomac Boat Club member. "I guess you could say it's addictive, but in a positive way."

In addition to exercising the arms, legs and torso, rowing offers one of the most stamina-boosting workouts around.

"I was a runner and decided I needed a change," says 25-year-old Phil Yeich, a lanky graduate student in chemistry at American University. "I definitely missed competing and racing, but didn't want to go back into running because I'd been doing it for so long."

A member of the Capital Rowing Club, Yeitch says he's aiming to race in national regattas this summer.

Many people take up rowing later in life. "I got involved as a parent in support activities for my rowing kids," says 49-year-old Kitty Porterfield of Alexandria. "I kept seeing the boats going by and decided I wanted to be in one."

Never having been involved in athletics before, the director of a nonprofit organization is now also a vice president of the U.S. Rowing Association. Porterfield says she rows regularly at the Occoquan Boat Club at Sandy Run Regional Park in Fairfax Station.

Some row for the beauty of the sport. "I'm a contemplative rower," says Ben Lamberton, a 50-year-old lawyer who has been rowing for four years. "The main reason I row is just to push off the dock and be alone. Rowing for me is just pleasure and play."

A bottleneck that hampers local rowing is the lack of river access. Local rowing advocates are pushing the National Park Service, owners of most of the Potomac shoreline, to allow more boathouses. "Rowing is going to grow. People realize that it is the sport of the '90s," says Fitzgerald.

Instruction in both sweep rowing and sculling is available in the Washington area. While a smooth stroke takes many hours of practice, the basics can be picked up in a few sessions. Beginners learn in wide, stable boats to avoid unplanned swims. Only when rowers become more poised and steady in their stroke technique do they graduate to the narrower racing shells.