Sure, you want to go to the beach, and yeah, you want to feel the sun on your hide, but Ocean City, gosh, is more than three hours away, and not exactly, when you get right down to it, what your soul is craving. What you want, though it defies your mid-Atlantic logic, is a combination of the mountains and the beach, a wacky sort of Pacific cocktail of scenery and swimming. But the Pacific is even farther than Ocean City and is also, at least in the American parts, generally too cold for a decent swim anyway. And you're low on funds and want some beach action THIS INSTANT . . . and you've already, on our savvy advice, been out to the Hammerman Area. Convinced that there aren't any good swimming spots left? Think you're doomed to another afternoon of running through the sprinkler? Well, think again, wanna-be wader, for Greenbrier State Park, in relatively nearby Washington County, is ready to welcome you into its cool, calm waters. Located in Boonsboro, which is, give or take, about 90 minutes from downtown Baltimore, Greenbrier State Park, it's true, is not exactly right around the corner. But we think that the park's wide array of recreational amenities, including a 42-acre man-made lake, a sandy beach and hiking trails (not to mention a pleasant playground), more than make up for the distance. Plus, you can't go wrong with the mountain views, especially the ones you can enjoy from the water. Rent a paddle boat, if you're feeling adventurous (and if you're planning on paddle-boating with little kids, you'd better be ready for a big adventure); take a stroll along one of the lovely wooded trails; or just hang out on the beach. However you spend your time at Greenbrier, chances are that it's going to be relaxing. And for premium relaxation, consider visiting on a weekday. You'll pay less for admission, find better parking opportunities, and not have to share the beach and lake with a zillion other people. And for still greater relaxation, consider pitching your tent at one of the park's 165 camp sites. There's a camp store, where you'll find plenty of convenience items, including snacks, and plenty of nature and the aforementioned playground to keep the kids busy. As if the lake - the shiny, refreshing, wonderful lake - won't keep them (and you) busy enough.