THIS TIME of year, Washingtonians are afflicted with an uncontrollable compulsion to leave their air-conditioned living rooms, their VCR flicks, the ballgame or the Sunday crossword puzzle, to observe an ancient ritual called "going for a cool dip."

That usually means one of two things: (1) joining a four- or five-hour caravan to the ocean where you plunk down, say, $80 for a night's stay in Motel Plastique; or (2) spending an afternoon at the community pool where you cower in a corner as far away as possible from the swim team practice.

Well, folks, there's no need to sweat it anymore. There's a third option: Just an hour or two from Washington are scads of attractive swimming spots -- in the Potomac River, Chesapeake Bay and assorted lakes -- only one of which requires a trip across the dread Bay Bridge.

You can find an old-fashioned, seedy boardwalk beach; a beach on the rebound; a beach spilling over with children; a beach where boy meets girl; or a clear lake so quiet you can hear a roasted marshmallow drop.

(The Chesapeake Bay and Potomac River beaches have more a seashore atmosphere than do the lakes, but be forewarned: Sea nettle season is upon us. Some beaches have nettle nets, but even they don't do the job completely. So if you're prone to allergic reactions, you might be better off heading for fresh water.)

On the other hand, who says "going for a cool dip" means you actually have to get wet? Anyone knows bodies searing in the sun always outnumber those in the water. And besides, much of the pleasure in visiting many of the beaches we have in mind comes from the trip itself -- down country roads and through friendly Beaver Cleaver towns.

To get you pointed in the right direction, here are nine nearby beaches worth exploring. (Times and prices are through Labor Day, for daytime visitors.) CHESAPEAKE BAY

SANDY POINT STATE PARK

Take away the brown pebbly sand, replace it with the golden powdery stuff, and it could be Ocean City. Teens in Hawaiian print trunks ogle bikini-clad lasses through cool-dude mirrored glasses; radios blare rock tunes; copper-skinned lifeguards keep watch over the kids bobbing chest-high in the water; a loose beach ball bounces onto a snoozing sunbather.

There is one major difference, though: The Bridge. Right out there where you can keep an eye on it.

Sandy Point, about eight miles east of Annapolis, is the best place in the world to relax and rejoice that you're not in that line of traffic droning over the Bay Bridge. Go ahead. Thumb your nose at the 18-wheelers. They're not so intimidating when they're two inches high and creeping along in slow motion.

You have a choice of East Beach or South Beach -- both equally crowded, both with parking lots and bath houses. On the bend that connects the two sections, the shore boulders conjure up a bit of Maine; neophyte windsurfers take their tumbles; and photo buffs can snap shots of the old lighthouse and ocean vessels traveling to and from Baltimore.

Other diversions: the marina where fishermen can rent boats, check the bulletin board for best bets of the day and read enviously about people who have caught some real lunkers; the tree-shaded picnic grounds and hiking trails; the fishing pier where, advises one savvy couple, crabbers can find happiness with "anything yucko -- chicken backs or wieners." SANDY POINT STATE PARK -- Amenities include snack bar and beach shop. No nettle nets. Arrive early weekends; the lots often are full by afternoon. Park is open seven days a week, 6 to dark for swimmers, 24 hours a day for fishermen and boat launchings; lifeguard on duty 11 to 5. Admission is $4 a car for Maryland residents, $5 for others; half-price Wednesdays; over 62, free. Directions: From the Beltway, take U.S. 50 and follow it all the way to Sandy Point. Watch for the turnoff on the right just before reaching the Bay Bridge. About 30 minutes from the Beltway. Call 301/757-1841.

NORTH BEACH

It's small, it's rocky, it's unnetted, but North Beach, next to Chesapeake Beach, Md., is one of the few free-admission beaches near Washington. And it's a chance to witness the budding resurrection of a town that was an eyesore not too long ago.

A fashionable resort that drew trainloads of vacationers in the '20s and '30s, North Beach more recently had become home to rotting waterfront fishing shacks. Federal grants for a new boardwalk, seawall and other improvements have brought fresh life. And for the past few years, newcomers and older families alike have been sprucing up with paint, new siding, window boxes and jalousied porches.

Gone are the pool hall and bar that had become hangouts for down-and-outers. More prominent these days are the handful of shops like Nice and Fleazy Antiques, Elvira Antiques, Fresh Air (designer jeans) and The Ceramic Ladies. In June there was a first-ever home and garden tour, and on August 23 the town is throwing its third annual North Beach Bay Festival. The piece de resistance: The old boarding house, Westlawn Inn at 9200 Chesapeake Avenue, is now a refurbished bed and breakfast inn (call 855-8410).

Don't expect an Old Town Alexandria. The town is still slowly on the mend. And, come fall, its face should change dramatically, with the boardwalk lengthened and broadened, a gazebo park and Victorian concession stands. Planned for future seasons: nettle nets, white sand, a wildlife observation park.

Meanwhile, the long, bumpy, boulder jetty near Chesapeake Beach remains a marvelous spot for viewing the endless Bay, water birds and fishing boats. The water is shallow and best suited for young swimmers. If you visit on a Sunday morning, you might want to grab a window seat and feast on the breakfast buffet at the Rod N Reel (9 to 1, $6.95, call 855-8351). For steamed crabs, townies recommend Abner's.

NORTH BEACH -- The beach is open daylight hours seven days a week. Free admission. No lifeguard. From the Beltway, take Route 4 east, then Route 260 to the beaches. North Beach is on the left; Chesapeake Beach on the right. About 30 minutes from the Beltway. There should be on-street parking available in North Beach, but arrive early. It fills up weekend afternoons. 855-6681.

BETTERTON BEACH

Another beach in transition, and also offering free admission, Betterton Beach sits on the Bay at the mouth of the Sassafras River in Kent County on Maryland's Eastern Shore. You'll know you're in the right place when you reach the hilltop and see the water glimmering through a lacy screen of trees.

Good News: The water is "virtually nettle free" because of its low salt content, according to Sue Blackiston, director of Kent County Parks and Recreation.

Good News II: After years of simmering on a back burner, a new boardwalk, picnic pavilion, parking lot and stone fishing jetty debuted this summer. (Target date for a bath house is mid-August.) The coarse-sand beach draws mostly a quiet family crowd. Food concessions are still a dim gleam in planners' eyes, so for now it's picnicking only, in the pavilion on a hillside overlooking the beach.

A suggested lunch stop en route is the Old Wharf Restaurant just over the bridge at the marina in Chestertown -- fresh, flaky fish, cheerful servers, decent prices. Crossing the bridge into Chestertown is a visual treat -- a striking view of grand old Federal and Georgian homes, sprawling back lawns and wooden docks. BETTERTON BEACH -- Open daily during daylight hours. Free admission. Lifeguard on duty 10 to 6 throughout the summer. From the Beltway, take U.S. 50 across the Bay Bridge to 301 north, then Route 213 north all the way to Chestertown. Continue on 213 for five miles and watch for signs. Turn left on Route 561, and turn right on 298; go three miles and turn left on 292 which goes all the way to Betterton. About 90 minutes from the Beltway. 301/778-1948. LAKES

CUNNINGHAM FALLS STATE PARK

Getting to this park in the craggy Catoctin Mountains is certainly a good part of the fun from the moment you take U.S. 15 out of Frederick, rolling past grazing goats, white clapboard houses with wooden Dutch girls on the lawns, American Legion halls, old men rocking on front porches.

At Catoctin National Park, just before Cunningham Falls State Park, men in hip boots cast for trout in streams presidents have fished. Catoctin Park is the home of Camp David (which is off limits and can't be seen from the road).

The two small sandy beaches at Cunningham Falls border Hunting Creek Lake, a watery playground for multitudes of splashing children, half of whom spend hours on end in the roped-off area shouting "Marco" to the other half who reply, "Polo."

Their parents lounge under umbrellas or rent fishing boats -- a smart move, since it's not unusual to haul in a couple dozen bass, trout, crappies or bluegills in an hour. For free pearls of fishing wisdom, look up boat keeper George Kress.

A change of pace for the jockish is a tromp to the 78-foot-high falls. It's a bit of a climb in spots but the cool and shady trail wanders past clear streams for about three-quarters of a mile. After rainy periods, the streams rush and the falls gush. (The falls also can be reached by car.)

Among the amenities: camping, lifeguards, bath house, grills, picnic benches and a snack stand inside a stone lodge, with hot and cold sandwiches from $1.25 to $1.95.

Dining Tip: Just south of the park is the Cozy Restaurant, off U.S. 15, in Thurmont. It's touristy, for sure, but fun anyway with its funky assortment of antiques and Main Street memorabilia. A bargain breakfast buffet is set out Saturday mornings for $4.50.

CUNNINGHAM FALLS STATE PARK -- Open 8 a.m. to sundown daily. Admission: $4 a car for Maryland residents, $5 for others; half-price Wednesdays; over 62, free. From the Beltway, take I-270 to Frederick, U.S. 15 north to Thurmont, then Route 77 west out of Thurmont to Catoctin National Park, and follow signs to Cunningham Falls State Park. About 1 1/4 hours from the Beltway. 301/271-7574.

GREENBRIER STATE PARK

This tree-fringed hideaway on South Mountain in Maryland's Washington County is the sort of place where a bunch of young adults might organize an impromptu volleyball game, but the most prevalent occupation by far is lazing -- on the sand, on a grassy slope, on a hammock stretched between tall, skinny maples. Every now and then someone gets up to turn over a chicken thigh smoldering on a grill. Nonconformists who insist on moving around can swim in the 42-acre, spring-fed lake, rent a paddle boat, fish from a rented rowboat or explore the Appalachian Trail, which passes through the park.

Trip Tip: Cut over to Alternate U.S. 40, going or coming, and visit nearby Washington Monument State Park (free admission) and climb up to the rugged stone tower, the first memorial dedicated to George Washington, in 1827. What a climb. What a view. Along the same route are pretty little towns like Middletown and Boonsboro (striped awnings, rose trellises and sidewalks that double as front porches).

Among other Greenbrier drawing cards: lifeguards, snack bar, bath house, camping.

GREENBRIER STATE PARK -- Open 9 a.m. to 7 p.m. daily. Admission is $4 a carload for Maryland residents, $5 for others; half-price Wednesdays; over 62, free. From the Beltway, take I-270 north to I-70 west to exit 42, right onto Rte. 17, then left on U.S. 40 west; park is just ahead on the left. About 70 minutes from the Beltway. 301/791-4767.

LAKE ANNA STATE PARK

Mom floats dreamily on an inflated raft, a paperback novel resting on her stomach; Dad stretches out on a lounge chair; their toddler digs a mound of sand out of the water and builds a soggy tent. A pair of teens plays catch with a Frisbee. No other human is in sight.

Lake Anna State Park in Spotsylvania County, below Fredericksburg, Va., is not a formal beach per se, but swimming is allowed at this 2,000-acre park with 8 1/2 miles fronting the lake. The water is so clear you can see rocks and vegetation on the bottom. Hiking trails snake in and out from woods to shoreline.

Some swimmers dive off grassy banks, but the best place for swimming, especially for children, is to the far left of the boating area where there's sand on the bottom and a gradual slope into the water. No bath house; no guards; no swimming near the boat launches; no concession stand.

Pluses: It's uncrowded, fishing folk (who wave and smile at hikers) seem to love the place, the visitors center has helpful staff and nature displays, the restrooms sparkle, there are plenty of grills, picnic tables and boat ramps. There's no concession stand.

Dining Tip: Steve's Family Restaurant, near the Spotsylvania County government buildings on Route 208 -- enormous, juicy gyros with the filling hanging out, at near-giveaway prices.

Trip Tip: Take Route 1 south of Woodbridge instead of I-95. It doesn't take much longer and has much more to offer in the way of sights: a roof made of hubcaps, trading posts, the thimble-sized Dumfries Town Hall, a super billboard touting Super Big Gulp.

LAKE ANNA STATE PARK -- Open dawn to dusk daily; visitors center, 10 to 6. Admission is $1.50 a carload; $2 for car with boat. About 80 minutes from the Beltway. From the Beltway, take I-95 or U.S. 1 south. If you take U.S. 1, take Route 208 west below Fredericksburg; if you take I-95, take Route 606 west out of Thornburg, then Route 208 west. Follow 208 to a right on Route 601, where there is a state park sign; follow 601 3.3 miles to the park entrance. 703/854-5704 or 703/854-5503.

POTOMAC RIVER COLONIAL BEACH

Shades of our dear old, down-at-the-heels amusement parks of yesteryear, Marshall Hall and Glen Echo. Their style lives on at this town in Westmoreland County, Va. The sand, pier and water almost take a back seat to the first thing that meets the eye: Big Hearted Jerry's carnie rides (usually open weekends, but sometimes BHJ takes to the road). For 75 cents, a youngster can brave a ride or a journey into the unknown world of the Ghost Busters Spook House.

If that isn't thrill enough, the banana-yellow water slide beckons at the other end of the wee boardwalk. The walk isn't actually wood, but concrete stained with the greasy ghosts of treats served up from small stands that open at whim -- clams, crabs, fries, cotton candy, burgers, corn dogs, popcorn.

If Big Hearted Jerry or the junk food vendors don't separate you from your mad money, maybe Jim Metheny of Boardwalk Boat Rentals will. You're sure to be convinced a ride on his sailboats, paddle boats, windsurfers or canoes is a steal at $3 or $4 a pop.

Meanwhile, back to the rest of the booths: Video games bleep and blink, pool shooters swap small wagers, shoppers mosey into the novelty store below the spiffy red-and-white Rock's Hotel where the clerk takes messages for roomers while ringing up sales. Above it all, painted on a rooftop, is an invitation to relax-eat-dance at Hop's Place.

Across the walk at Reno on the Boardwalk, perched on a pier over Maryland waters, a late morning line forms for state lottery tickets. Most of the excitement is on weekends when a flea market often is set up next to the amusements. Other coming events: a craft show from 11 to 5 on July 26 and 27; a fine arts show from 11 to 5 on August 9 and 10.

The beach has nettle nets and new sand, imported after a storm last fall.

COLONIAL BEACH -- Open daily during daylight hours. Lifeguards. Free admission. From Virginia, take I-95 or U.S. 1 south to Fredericksburg, Route 3 east to Route 205 east to the beach. From Maryland, take Route 5 off the Beltway; them U.S. 301 south and across Nice Bridge to Route 218 east; then Route 205. About 1 1/2 hours from the Beltway. For information, call the Chamber of Commerce at 804/224-7531.

FAIRVIEW BEACH

Although this site is primarily for campers, daytrippers are welcome to swim and use the bath house at Fairview Beach, 13 miles east of Fredericksburg, Va. Going full speed on the same complex are a crab house and water slide. The best way to watch the passing parade of sunners, swimmers, rubber rafters, boaters, water skiers and windsurfers is with a cold drink on the wooden deck that wraps around the crab house (food served noon to 9, drinks until midnight).

From noon to 8 on weekends a canopied water shuttle transports boaters from their anchored craft to the restaurant. The water is clean, the sand fine and golden, the shoreline thick with trees and a lovely home or two. Nettles aren't a problem here, says owner Vic Mason: "I rarely have seen one in the past 10 or 15 years -- the water isn't salty enough for them." The beach, open daylight hours, is unguarded but the water is shallow up to the pier.

FAIRVIEW BEACH -- Open daily during daylight hours. Admission (not including water slide): $2.50 adults, $1.50 children, free under 3. From Virginia, take I-95 or U.S. 1 to Fredericksburg; then Route 218 east to Route 696. Watch for the beach sign. From Maryland, take Route 5 off the Beltway to U.S. 301 south, cross Nice Bridge and follow 301 to Route 218 west to Route 696. About 75 minutes from the Beltway. 703/775-7500.

POINT LOOKOUT STATE PARK

One of the prettiest (and, alas, most crowded) beaches, this park is in St. Mary's County in southern Maryland. The grass next to the fluffy sand is equipped with its own natural shade-tree "beach umbrellas." For a truly lost-in-space feeling, before entering the park take a drive all the way to the Point. The strip of land is so narrow the highway serves as a common road for the swimming beach on the Potomac and the boating area on the Chesapeake.

The guarded swim area has nettle nets, but they're not completely successful. "They get pretty bad here," says staffer Brenda O'Neill. Among offerings: a Civil War museum, bath house, grills, picnic tables, playground equipment, boat rentals, hiking trails, camping. There's no snack bar.

Lunch Tip: Sit out on the deck at Duffy's Tavern, at nearby Scotland Beach (just beyond the park turnoff from Route 5). But first step inside and say hi to an institution in these parts, Mom Duffy, playing bartender/cook/waitress amid the hodge-podge: joke shop signs everywhere; families attacking heaps of crabs on faded-plastic-covered tables, their voices competing with country music on the radio. Ask about Mom's homemade bread. Locals also recommend the restaurant at Scheible's Fishing Center in Ridge, five miles north of Point Lookout.

Arrive early on weekends; the park fills up.

POINT LOOKOUT STATE PARK -- Open daily 8 a.m. to sunset, guarded 10 to 6. Admission: $3 a carload for Maryland residents, $4 for others, half-price on Wednesdays, over 62, free. From the Beltway, follow Route 5 (the scenic route) all the way to the Point. About 70 minutes from the Beltway. 301/872-5688.

Irene Heath is a Washington writer.