Joanne Ivancic was sitting in the dead heat, half an hour after the first, hopefully annual, Potomac Cup Boardsailing Regatta was scheduled to begin, wondering how much it would cost to rent a fleet of helicopters to whip up a breeze.

"I'm praying for some wind," said Ivancic, who was behind a registration table in West Potomac Park over the weekend, only 20 yards from the Potomac River. "There's not even enough wind to move the weeping willows."

Boardsailors don't need much of a breeze to sail on. Their boats, and there is more than a little debate over using that word to describe them, are basically oversized surfboards. They are about 12 feet long, weigh only 40 pounds and support a relatively huge area of sail. From a distance of 100 yards, boardsailors appear to be holding the mast of a sinking ship.

But these days, at least on the Potomac, boardsailors insist on using the word boat to describe their sailing corks. The reason for that has more to do with the District government than respect for nautical precision. If they are not boats, then they must be boards. And in that case, they would not be allowed on the Potomac.

In 1972 The D.C. City Council banned all sports on the Potomac that involved "purposeful contact" with the polluted water. The list included swimming and water skiing. Boardsailing, which was only invented in the late 1960s, was not popular here at the time.

During the last four years, however, since Bob Singer and Ron Fogan introduced the sport to the area, boardsailors and the D.C. Police Department's Harbor Patrol have been at odds over just how wet the sport really is.

"We're saying it's not a water-contact sport," said B.J. Cunningham, who has been teaching boardsailing on the Potomac for two years. "There's really not much difference between a sunfish and a sailboard."

A few years ago some boardsailors, including Paul Pinkney, 72, of Philadelphia, staged a Fourth of July protest on the Potomac to prove Cunningham's point. Wearing three-piece suits and carrying attache cases, the boardsailors eluded police and rode the wind across the Potomac.

For now, boardsailors are allowed to ride the Potomac between Chain Bridge and Wilson Bridge. But the issue has not been fully resolved. The City Council is expected to take up the matter again in the next few months. In the meantime, the sailboards are considered boats and must register with the harbor patrol and must sport identifying numbers.

"So far they haven't forced us to carry navigation lights, portable johns or fire extinguishers," said Bob Kozak, another organizer of the weekend regatta that donated all entry fees to Children's Hospital.

Underlying the boardsailing debate is another involving the Potomac. When the City Council banned all water sports 11 years ago, the river was little better than a giant sewage drain.

Since then, more than a billion dollars has been spent to clean up the Potomac. You can see, and smell, the improvement. But District health officials, including Jim Collier, chief of the District's water hygiene division, warn that the river is still not clean enough for safe swimming.

One problem with the Potomac is the 100-year-old system of District sewers that overflow after a storm, dumping sewage directly into the Potomac. Some of those pipes feed into the Potomac directly above and below the Thompson Boat Center where Cunningham teaches the sport.

"I've never had any complaints," said Cunningham, waiting with a dozen other boardsailors for the start of the regatta. "There's no chance at all of hepa-whatsis from that water. Of course, I wouldn't advise anybody to drink it."

The amount of contact made with the water in boardsailing depends on who is riding the board. For beginners, an occasional dunking seems unavoidable. And even the best boardsailors will tip occasionally. A boardsailor who never takes a dive probably isn't trying hard enough. It is that proximity to the elements that has made the sport such an overwhelming success. Though only 15 years old, the sport has grown so rapidly it will be included in the 1984 Olympics. By comparison, baseball has never been more than a demonstration sport in the Olympics.

Peter Shafer, 18, a Northern Virginia Community College student, is one of the newest converts to the sport. Until he took a lesson during a vacation this summer, Shafer was wedded to a conventional Laser sailboat.

A few weeks ago Shafer spent $1,200 for a boardsailor.

"I haven't sailed my Laser since," he said.