As swamps go, Battle Creek Cypress Swamp is wet, wild and perfectly dismal. Bald cypress trees, draped in poison-ivy vines, rise straight and thick from a watery ooze. Most of the year, when the sun is blocked by a dense cover of cypress needles, this looks like a place where Tarzan might get caught in quicksand.

The only thing this swamp lacks is a slimy, web-toed creature to haunt it and Dwight Williams is working on that.

"One of these days we'll have a contest, have the kids who come here draw their favorite swamp monster," says Williams, the caretaker of this nature center and soggy preserve that seems too tropical to be just 45 miles southeast of Washington.

The Cypress Swamp is one of 10 chunks of land in Maryland that have been preserved by the Nature Conservancy, a non-profit, national conservation organization. Thanks to the Conservancy, there are thousands of acres of wetlands, hardwood forests, Great Blue Heron sanctuaries and boreal bogs in Maryland that might otherwise be video arcades and parking lots.

While endangered species bite the dust everywhere and the Interior Department holds bargain-basement sales on America's last frontiers, the Conservancy's work is an encouraging reminder that there are some environmental struggles being won.

Last week the Conservancy announced a $50-million, five-year effort to conserve American wetlands, after the Richard King Mellon Foundation provided a $25-million grant, the largest ever made by a private foundation for conservation purposes. The Washington-based Conservancy must raise the other $25 million.

"The water-related ecosystems which the National Wetlands Conservation Project aims to conserve are among the most important but endangered natural systems in the country," says William D. Blair, Jr., Conservancy president.

The Conservancy was formed in 1951, primarily to protect small, park-type properties in the Northeast. It since has undertaken about 3,000 projects in Latin America, Canada, the Caribbean and all 50 states. The Conservancy has purchased 576,000 acres, and provided assistance in buying or managing a million more. The Conservancy currently manages 700 wildlife sanctuaries in 47 states.

For a firsthand look at what the Conservancy does, take a tour of Maryland. Begin at the state's western edge, at the Cranesville Swamp in Garrett County. On its 313 acres is the southernmost tamarack forest in the United States, rich in Ice Age plant life, bobcats, otters, brook trout and snowshoe hare.

By the time you get to the opposite corner of the state, across the Chesapeake Bay to the Nassawango Creek-E. Stanton Adkins Preserve in Worchester County where flying squirrels perform from loblolly pine trees, you will have seen examples of almost every dominant ecosystem found in this country.

The Battle Creek Cypress Swamp in Calvert County is the closest of the Conservancy's preserves to Washington. It is just a few miles west of Rte. 4 past Prince Frederick. Surrounded by swamp, you feel much farther away.

"This was the first preserve the Conservancy acquired in Maryland," says Williams, Battle Creek's "swampologist" and builder of the quarter-mile long boardwalk that carries visitors on a loop through the swamp.

"In the 1960s this area was listed as a tourist stop in Calvert County, but there was nowhere to go to see it," says Williams, who has been a full-time naturalist at the preserve, his salary paid by Calvert County, since 1977. "There is a bridge across the stream bed and cars would stop in the middle of the road to peer over it."

Now 10,000 visitors a year walk the boardwalk, a few feet above the swamp, looking at mud turtles and woodpeckers and the roots of cypress trees that jut out of the water every few feet like nobby knees.

Battle Creek got its name from Calvert's original county seat, Battle Town, which was built in the late 1600s where the creek empties into the Patuxent River. It was named after a town in England rather than a Revolutionary War battle.

"That's very disappointing to third graders," says Williams, after showing a visitor the soggy delights his small kingdom offers. "Someday I'll have to make one up."