There's something about opening fresh oysters outdoors in the crisp, clear autumn air and eating them in an Eastern Shore town near their native waters that makes them seem much tastier than any store- bought mollusks.

Last November, I was doing just that -- at Easton's annual WATERFOWL FESTIVAL. I was standing in the parking lot of Hopkins' real estate, which, like most of the town's businesses, was decorated for the festival, to be held November 12-14 this year. Life-size wooden geese, surrounded by dried stalks, grasses and fresh greenery, were displayed on the front porch. Cutouts of flying geese hung from the porch ceiling and blew gently in the early November breeze. Sounds of geese, ducks and splashing water completed the display, thanks to a tape recorder Hopkins had hidden in the rushes.

On the adjacent lot, plank tables, rubber gloves, oyster knives and bushels of oysters -- freshly harvested from nearby Tilghman's Island -- awaited festival-goers who accepted the realtor's generous offer. All you had to do was shuck them, and Hopkins' expert, friendly advice made that seem easy: Hold the shell firmly on a plank table with your left hand. Take a round, wooden- handled oyster knife in your right hand and slip it into a seam in the shell. Run the knife around the seam and slit the rough, ridged shell in half to expose a glistening oyster.

Thousands of hands will be shucking oysters on Maryland and Virginia's Eastern Shore this fall, the peak season for oystering. To celebrate this harvest from the sea, many places on the Eastern Shore hold fall festivals where the oyster's a mainstay on the menu.

Eastern-Shore food specialties are also for sale at Easton's Waterfowl Festival. Last year, Kiwanis Club members manned a cleverly decorated outdoor booth called The Duck Blind, serving crabcake sandwiches and fried clams. Lions Club members sold oysters -- steamed and on the half-shell -- and ladled out steaming-hot, thick crab soup and oyster chowder. The Waterfowl Festival also features waterfowl art -- paintings, photographs and prints, duck stamps, an auction of antique decoys, a duck- and goose-calling contest and workshops where artists and carvers give demonstrations.

Chincoteague oysters, famous for their distinctive flavor, are celebrated in real style in Chincoteague, where oystering has dominated the economy for three centuries. At the OYSTER MUSEUM OF CHINCOTEAGUE I learned that Indians were Virginia's first oystermen, and that the Jamestown colonists' first meal on Virginia's shores was an Indian oyster roast appropriated by a landing party of colonists who scared away the natives.

A beautifully detailed exhibit in the museum explains, with lights and sound, how Chincoteague oysters come from their home in the sea to the homes of oyster-eaters. The story begins with spotlights on a miniature three-dimensional model of an oysterman's boat. "Harvesting takes place in fall and winter seasons here," the narrator explains. "In shallow water, tonging for oysters is done by hand much the same way as it has been for hundreds of years. In deeper waters the catch is taken by dredges, which are operated either by hand or mechanical power."

The exhibit shows a scow-type boat (used in shallow waters) passing the marshes where the famous Chincoteauge ponies roam wild and free. The boat, loaded with seed oysters, is heading for one of the underwater grounds where the oysters will be re- seeded. When these oysters are about four or five years old, the oysterman will gather them up during the fall harvest. Many implements used in seafood farming are displayed in the museum.

In the exhibit's final scene, there's a cutaway model of an oyster-shucking house where workers are shown shucking the oysters by hand -- there's no mechanical method yet perfected to remove an oyster from its shell.

Until I visited the Oyster Museum, I'd thought oysters should only be eaten during "R" months. A museum exhibit explains that this popular belief arises from the fact that oysters aren't very tasty during the spawning season, which is supposed to last from May 1 to September 1. But the actual spawning season varies throughout the world, so oysters are obtainable in prime quality every month in the year.

As for quality, the display notes that probably no other food is raised under stricter government controls than oysters. The sanitary conditions of cultivation, production, handling at the shore, transportation and marketing are rigidly supervised. The museum is open fall weekends until Thanksgiving, and by special arrangement for school and tour groups. (Call 804/336-6117.)

Visiting the museum, driving or biking to nearby Assateague Island to see the famous Chincoteague ponies and thousands of colorful and unusual waterfowl in the NATIONAL WILDLIFE REFUGE, and strolling along the beautiful ocean beaches at ASSATEAGUE ISLAND NATIONAL SEASHORE, are some of the other pleasures awaiting visitors to Chincoteague.

At CHESAPEAKE APPRECIATION DAYS, October 30 and 31, Maryland's oyster-dredging Skipjacks, the last working sailing fleet in North America, will compete for the "Top Skipjack" title off Sandy Point State Park, near the Chesapeake Bay Bridge. On TILGHMAN ISLAND DAY, November 6, visitors can board the boats, talk to the captains and see how seafood is harvested. There'll also be net- making demonstrations, workboat races, and boat-docking contests. Oysters, served in all the usual styles, will be available at both these events.

Highlights of the 25TH ANNUAL OYSTER FESTIVAL,in Urbanna, Virginia, to be held November 5 and 6, include a parade, November 6 at noon, featuring the 1982 Oyster Queen and the 1982 Little Miss Spat (named for baby oysters), and a seven-mile run for all ages (entry deadline is that Saturday morning). An oyster dinner will be sold at the Urbanna firehouse, and oysters, fried, frittered, raw, roasted, steamed and stewed, will be sold at booths during the festival, which drew 30,000 people last year. EASTERN SHORE OYSTERING

Plan ahead if you want to stay overnight during these festival weekends. Most festivals are a relatively easy and short drive from Washington, making them ideal day- trip outings. 18TH ANNUAL CHESAPEAKE APPRECIATION DAYS October 30 and 31, Sandy Point. For information: Office of Tourism, 1748 Forest Drive, Annapolis 21401. Call 301/269-3517. 11TH ANNUAL TILGHMAN ISLAND DAY, November 6, 10 to 5, Tilghman Island. For information David McQuay, Tilghman Island, Maryland 21671. Call 301/745-5330. 25TH ANNUAL URBANNA OYSTER FESTIVAL, November 5 to 6, 10 to 6, Urbanna, Virginia. For information: Urbanna Chamber of Commerce, 840/758-5540. THE WATERFOWL FESTIVAL, November 12 to 14, Easton. For information: Waterfowl Festival Headquarters, The Tidewater Inn, 609 South Washington, Easton, Maryland 21601. Call 301/822-6314.