Pools can be fine for lap swimming but not so fine for communing with nature, and then there's the chlorine. The ocean is three hours away -- hardly a day trip -- and when you get there the boardwalk's crowded and you have to battle to establish a beachhead beneath an umbrella.

If you've had it with both pools and ocean, there are other possibilities: lakes, rivers, the Chesapeake Bay, farm ponds and just plain swimming holes. You can make a day of it in a state park at a lake surrounded by tall trees or mountains, and be home by dark. You can float in a farm pond, if you're friendly with a farmer, or in a good old swimming hole in a creek.

A fisherman I know likes a dip in ANTIETAM CREEK near Sharpsburg, Maryland. You find bends in the creek, and behind a good bend will be a dip, a swimming hole five or six feet deep, he says. Anglers hang their lines over the little stone bridge between Keedysville and Sharpsburg. "It's all shaded, looks like green mansions," he says. "If you like black snakes, it's great."

To each his own. Go west and you'll find a cool country lake in GREENBRIER STATE PARK in Washington County, Maryland. Admission to this and other Maryland State Park beaches is $3 a car on weekends, holidays and weekdays, except nonholiday Mondays, when it's free.

Ten miles east of Hagerstown along U.S. 40, Greenbrier offers camping, fishing, hiking, picnicking and canoeing. Swimming is in a 42-acre lake with a wide sandy beach and modern bathhouses. The Appalachian Trail passes through the park, but for the less ambitious, there's a short, self-guided nature trail. Phone: 301/739-7877.

Closer to home in Frederick County, CUNNINGHAM FALLS STATE PARK near Thurmont is special for a lot of reasons besides swimming, fishing and canoeing in Hunting Creek Lake. There's the waterfall, along with nature trails and the remains of the Catoctin Furnace ironworks. Starting in mid-June, interpretive talks are planned for Saturday afternoons at the falls and Sunday afternoons at the furnace. For more information, call 301/271-2495, or 301/271-7574.

After your swim you can eat a picnic dinner and then drive over to CATOCTIN MOUNTAIN PARK, adjacent to Cunningham Falls, to sit around a campfire. The campfire program happens at dusk on Fridays and Saturdays in Owens Creek Campground. For other diversions, starting the end of June, the Blue Blazes Whiskey Still will be running weekends from 11 to 5. The still replicates on a smaller scale the moonshining that happened in Catoctin Park in the 1920s. A park map can be picked up at the Visitor Center. Phone: 301/824-2574.

Though there are a few lakes around Baltimore, Barbara Newnam, who does public affairs for the Maryland State Parks, recommends that Washingtonians try Greenbrier State Park rather than fight for space on beaches that serve the Baltimore population. GUNPOWDER FALLS, for example, is the only state park in the Baltimore County area that offers swimming.

On the Chesapeake Bay, SANDY POINT STATE PARK, on U.S. 50 just before the Bay Bridge, gets busy as well. Two weekends ago, Newnam says, the park reached capacity by 2 p.m. on Sunday and closed its gates. So be prepared for crowds. It has a boat ramp, picnic grounds and two beaches. Phone: 301/974-1249.

Besides Sandy Point, in the Annapolis area there's also BAY RIDGE BEACH AND POOL, privately owned, with 1,800 feet of sandy beach on Chesapeake Bay. On Herndon Avenue in Annapolis, it also has two swimming pools, bathhouses and a snack bar. Admission on weekends: $3.50 for adults, $2 for children. Phone: 301/269-0858.

Between here and Baltimore, there are FORT SMALLWOOD PARK and KURTZ BEACH. Fort Smallwood has a sandy beach on an inlet of the Bay. Owned by the city of Baltimore, the park offers bathhouses, picnic areas, playground, fishing. Admission is $2 a car; small additional fee for swimming. It's on Fort Smallwood Road, north of Annapolis and east of Glen Burnie. Phone 301/255- 5885. Kurtz Beach is on the Patapsco River in Pasadena, Maryland. It has bathhouses, picnic tables, a playground and a snackbar. Admission on weekends: ages 12 and over, $2.50; ages 6 to 11, $1.50, under six free; senior citizens $1. Phone: 301/255-1280.

Turning south, about two hours' drive from Washington, POINT LOOKOUT STATE PARK is at the very tip of St. Marys County in southern Maryland, where the Potomac River joins Chesapeake Bay. Once the site of a federal Civil War hospital and prison, Point Lookout is now a place for swimming, camping, crabbing, fishing, boating, hiking and biking. If you happen to visit on June 12, don't be surprised by the Confederate soldiers. They're just reenacting in celebration of Confederates' Day. The park is reached via Route 5. Phone: 301/872-5688.

The word on this and other Bay beaches is: get your swimming in before the Fourth of July. Don Hammett, a ranger at Point Lookout State Park, says that the occasional sea nettle around July 4 will start keeping people from the water. This is not to say the swimming stops. On overcast days when the wind is blowing, says Hammett, the stinging nettles cease to be a threat: the current pulls them out to sea, or they drop to the bottom. "They don't like to be jostled around," he says. Hammett recommends swimming on cloudy days; when the sun is out, try crabbing or fishing instead.

Finding a lake is "very difficult in Virginia," says Joanne Potts, director of the local office of the Virginia Travel Service. In the George Washington National Forest, she recommends SHERANDO LAKE near Waynesboro or TODD LAKE near Harrisonburg. But that's pretty far to go for a day.

East of Fredericksburg, WESTMORELAND STATE PARK has a beach area on the Potomac River and a new swimming pool as well. A visit to the park can be combined with a little history: It's between George Washington's birthplace and Stratford Hall, where Robert E. Lee was born. Two small picnic shelters with fireplaces, electricity and running water are available at the park, first- come, first-served; there's also a nature center, snackbar and restaurant. Admission is 50 cents per car; swimming costs $1.25 for adults and 75 cents for kids. Take I-95 south to Fredericksburg, then Route 3 east about 40 miles. The park is on the left. Phone: 804/493-8821.

From Route 3, a left turn on to Route 205 leads to COLONIAL BEACH, which is north of Westmoreland State Park. "It's old and a bit run-down," says Potts, "but people go there just to have a place to go, because they are few and far between in this area."

About 70 miles west of here, in the Shenandoah Valley and deep in the country, you'll find WAYSIDE WONDERLAND. On Route 11 near Middletown, Virginia, it's a privately owned 25-acre lake in what used to be a quarry, on 250 wooded acres. There's fishing, canoes for renting and horseshoes for throwing. The park is open only on weekends: Admission is $2.50 for adults and $1.25 for kids. Phone: 703/869-1797.

If you must pool it, do it up big: The Northern Virginia Regional Park Authority claims that its two swimming pools are the largest on the East Coast. At POHICK BAY, near Woodbridge, and BULL RUN, near Centreville, both pools measure a half-acre, with an equal amount of deck space. Swimming is $1.50 for adults, $1 for kids and 75 cents for senior citizens. Other features are picnic shelters, miniature golf and nature trails. No park entrance fee is charged to residents of Arlington County, Fairfax County and Loudoun County, Alexandria, Falls Church and Fairfax. Otherwise, it's $3.25 per car. Phone Pohick Bay at 703/339-6104; phone Bull Run at 703/631-0550.