Taylor Crandall stood on a floating dock, face to stern with a 65-foot, $500,000 sailboat, and submitted to sweet despair.

"Every year, I come to this boat show to suffer," said Crandall, a Baltimore computer programmer with an appetite for sailing ships that his budget cannot satisfy. He still comes to local boat shows just to look. And this weekend, at the U.S. Sailboat Show in Annapolis, Crandall has more than 500 boats to make him hungry.

"I can see myself at the helm of every boat here, sailing the world's great oceans and pulling into exotic ports," said Crandall at Friday's opening day of the show, which will continue until Monday at 6 p.m. "It's great while I'm here. But I'm usually totally depressed by the time I get home."

The yacht brokers, marine bankers and equipment manufacturers who have taken over the city dock and harbor for the country's biggest and most prestigious in-water boat show, don't mind the Crandalls in the crowd. By their yearnings, the fever grows. It helps them catch the real buyers in the crowd of about 100,000 expected to file past the boats before the show's end.

"The economy has picked up and people are buying. Financially, they quit worrying about it, went ahead and bought what they wanted," said Mark Brown, a blond, island-tanned salesman on Crandall's dream boat. Boat is a bit plain for the 65-footer, which comes equipped with air-conditioning, stereo sound and more modern conveniences than a World Fair home of tomorrow. "I don't know anybody who has a house nearly as nice," said Brown, who stood by the stern walkway asking visitors to kindly remove their shoes.

The boating industry, both power and sail, is booming. The stall that climaxed in 1980, when interest rates rose to 21 1/2 percent, has reversed itself. With rates near 13 percent, and lending institutions competing to make loans to pleasure boaters, buyers are once again submitting to the tug of the tides.

Nowhere is it easier to be seduced than Annapolis. Unlike most boat shows, where the potential customer must climb a ladder in some fluorescent-lit, convention center showroom, the Annapolis show lets you board boats that bob gently at a dock. The daylight ricocheting off the trim work and breeze blowing a song in the rigging make the outdoor fantasy a lot easier to sell.

When Jerry Wood put on the first Annapolis sailboat show in 1970, there were just 43 boats to drool over. It was the first time anyone had tried the in-water concept for a major fall show, so it took a while to catch on. This year, there are boats from Europe, Central America and the the Far East.

"I was here years ago, when there were not many boats," said Luke Churchouse, the English president of the Drascombe company that manufactures boats resembling old, New England life boats. "We were set up under a lovely tree that gave us some shade. I thought if this is Annapolis, I'm coming back every year."

It is not all sunny skies, however, for the boating industry. This year, the Environmental Protection Agency announced plans to drastically curtail the use of leaded gasoline. The change was aimed at motorists who have been cheating at the gas pumps. The EPA estimates that 13.5 percent of cars designed to burn unleaded fuel are running on cheaper, leaded fuel, which is known to leave more pollutants in the atmosphere. Beginning Jan. 1, 1986, the amount of lead permitted in gasoline will be cut by 90 percent.

The boating industry immediately cried foul.

"Millions of marine engines could be rendered obsolete practically overnight," BOAT/US vice president Michael Sciulla testified in August at an EPA hearing. There are an estimated 4.5 million boats that use high-compression marine motors designed to run on leaded gasoline. With the average cost of an outboard around $3,000, the EPA action could represent a $12 billion problem for boaters.

There are ways to "juice up" unleaded gasoline to power existing engines. But octane-boosting additives such as methanol can damage fuel systems by eating away at the gas lines. That, warns some experts, could lead to fires or explosions.

"They have got to give us the time to adjust our technology . . . we can't redesign the wheel in 60 days," Ron Stone, a lobbyist for the National Marine Manufacturers' Association, told the boating publication Soundings.