Season of Aquatic Adventures Makes Splash on 'Opening Day'

IT'S a Seattle-style parade, not poking along on pavement, but in Puget Sound. With costumed crews and loud music, a flotilla of yachts, amphibious cars, and jet skis makes its way past an admiring throng. Tugboats do pirouettes in the narrow passage connecting lakes Union and Washington. Seamanship more akin to McHale's Navy than to the America's Cup is evident along the route.

Here in the brisk waters surrounding Seattle, an annual provincial rite got under way last Saturday. The people of Puget Sound, crazy about getting out on the water, embark on aquatic adventures year-round, but this weekend was the official kickoff to the best and busiest half of the year. Boats are to Seattle what brownstones are to Boston and bagels to New York.

''It's one of the most beautiful places on earth for boating,'' explains Nila Laguana, who works at Dagmar's Marina in Everett, Wash. The region boasts inland lakes, island-studded Puget Sound, and entry to the inland passage to Alaska. Add a mild climate, mountains, and (until recently) abundant fish, and you have a premier aquatic playground.

One in 5 households in Washington State has at least one boat, with small power boats making up 40 percent of the total. The state also has the world's largest recreational-boat manufacturer (US Marine, based in Everett) and the world's biggest charter fleet.

On this ''Opening Day,'' sponsored by the Seattle Yacht Club, the theme is ''Best of the Northwest.'' Many boats give a nod to another regional obsession: gourmet coffee. One yacht's crew dresses as frothy cups of cafe latte; in another boat a man draped in a Central-American blanket tows a mock mule laden with burlap coffee-bean bags.

Many of the yachts, meanwhile, take a dignified tack, with crews lined up stiffly in blue blazers and white trousers or skirts.

Not all the excitement is planned. A boat called Obsession, trying to get its spinnaker up, gets the sail tangled instead. The picnicking, baby-strolling masses on shore sighs a sympathetic ''oh'' as the crew gathers the balloon-like sail, part of which sags into the water.

The first Opening Day was in 1909. Competitive rowing in the region goes back even further, though only in the last 26 years have races been part of Opening Day.

The crew races come before the parade, and are the day's highlight for many spectators.

For the rowers, who aren't accustomed to performing for 100,000 cheering fans, the crowd can be inspiring. ''There was so much noise,'' says University of Washington rower Hana Dariusova, that she can hardly remember when during the 2,000-meter race her boat caught up to Princeton University's varsity team.

From start to finish, the race course is lined with sail and motor boats on both sides, moored on log booms. Near the end of the race, the crew boats leave Lake Washington and enter narrow Montlake Cut, an ideal viewing ground for landlubbers.

Sitting in the ''stroke'' seat that sets the pace for seven other rowers, Ms. Dariusova led her boat to a two-second victory. The Princeton women had not lost a race in six years.

Sixteen races were held Saturday morning, in categories ranging from novice (freshman) to masters, over 50 years old.

''You still get the butterflies on the starting line,'' says the elderly Bill Cameron of the Ancient Mariners Rowing Club. The club calls him a RAM (really ancient mariner), while younger teammates are YAMs.

The day following all this excitement, volunteers from the Northwest Outdoor Center paddle sea kayaks around the lakes picking up floating trash. ''You'd be amazed what you find the day after,'' says the center's Merle Stephey.