Even the U.S. Navy agrees that the way to master big-boat handling is to practice small-boat handling. That's why the Naval Academy has such a busy little sailing fleet in Annapolis.

Boatman carries it one step further to assert that the best boat-handler is the one who can handle the smallest boat in the biggest water. He would lend his Mako anytime to the fellow who sailed from California to Australia in a nine-foot sloop, but he gets nervous sharing the gas dock with a cabin cruiser.

Follow this smaller-is-better credo to its logical end and you wind up with kayak and canoe whitewater racers as among the best boat-handlers of all, a claim hard to dispute.

Any doubters should have been down at Fletcher's Boat House last weekend to meet some local members of the 1983 U.S. Whitewater Team, which finished fourth at the world championships in Italy last month, and to watch videotapes of their wild exploits in cascading waters.

The occasion was the first Potomac Paddle-a-Thon, designed to raise money to support the team, which has many local members, and to back stream-saving efforts of the American Rivers Conservation Council. It was a success, raising about $4,000 to be split by the two groups.

One of the fund-raising devices was the auctioning of a new, 11-foot kayak donated by the manufacturer, Perception. The little red boat, called "Dancer" for its nimbleness in big water, appealed to boatman, who climbed in it to see how it felt.

It felt tiny. It felt weightless. He could barely get his big feet in, and once he did he felt as though he were sitting in a dart. There wasn't room inside for the basic necessities of life, which is to say a six-pack.

It was some sexy, little fast boat and boatman was aroused enough to ponder bidding. He decided to check first with some big- time racers to see if they shared his enthusiasm. He asked muscular Dutch Downey, who finished 23rd in the world championship in the wild-water solo canoe class, about it.

"It's pretty nice," said Downey, "for a cruising boat."

"Cruising boat?" said boatman, who felt he'd just stepped out of a Maserati.

Sure, said Downey. "When you're used to something that weighs 13 pounds, taking one of those things downriver is like driving a truck."

Downey and the Haller brothers, Fritz and Lecky, who won the gold medal in Italy in the two-man slalom canoe class, were manning a booth under a shade tree at the Paddle-a-Thon. They were showing videotapes of a whitewater classic, "Fast and Clean," about world-class racing.

The TV show is largely about Washington paddlers who comprise almost half the team. One of the stars is Jon Lugbill, the local solo slalom canoeist who has won the gold medal in that highly competitive class at the last three world championships.

Another star is David Hearn, who probably wishes Lugbill would develop a nice bone spur in his elbow. The world championships are held every other year. In 1979, 1981 and now 1983, Hearn has beaten everyone except Lugbill, taking second-place silver each time.

Hearn's sister, Cathy, was the gold medalist in women's slalom kayak in 1981, but this year finished seventh. Her teammates say she's back in hard training, shooting for a berth on the 1984 U.S. women's flatwater kayak racing team.

Other local winners at Merano, Italy, last month were Kent Ford, who joined Lugbill and David Hearn to take a gold medal in team solo slalom canoe; Mike and Steve Garvis, who won a bronze in two-man slalom canoe. The Hallers and Garvises also helped take the silver medal in team two- man slalom canoe.

One who didn't win anything until she got home was Elizabeth (Boo-Boo) Hayman, who finished 16th in the women's wildwater kayak event at Merano.

Hayman was one of about 50 paddlers who ventured onto the Potomac at the Paddle-a-Thon in an effort to raise money for the team and for conservation. With a long list of "sponsors" pledging donations for each mile she traveled, Hayman knocked back 13 miles on the steamy, flat river and earned close to $200.

For her effort, she won the Paddle-a-Thon grand prize, a 16-foot Mohawk canoe donated by Hudson Trail Outfitters. Boatman, aware now of how the hot racers despise "cruising" boats, clapped in appreciation and wondered what she'd do with it.

The Hallers made the presentation. They handed the big red boat over, but poor Hayman was laughing so hard she couldn't even lift it. BACK A PADDLER -- The U.S. Whitewater Team is about as underfinanced as a world- class team would want to be. Members trained six months for the world championship, abandoning school and jobs, then had to pay plane fare to Italy for themselves and their boats to compete. All the team was able to provide was $250 in expense money. The Paddle-a-Thon was a start in efforts to improve financing, said assistant coach Gordon Bare. He said the team is seeking individual and corporate sponsors through the Friends of the U.S. Whitewater Team, 6537 Broad Street, Bethesda 20816. Individual membership is $25, but Bare says donations in any amount are welcome.