ONE WOULD expect a flooded rock quarry to be turbid and dismal at best, but during a recent visit to the Millbrook Quarry off I-66 near Haymarket, Virginia, the clarity and turquoise hue of the water argued otherwise.

"Yeah, the water quality is pretty good," says Russell Post, who manages the seven-acre quarry that has become a magnet for area scuba divers. "It's fed by springs, and when the water is high it spills over into that creek, so it's not stagnant. You can see for about 35 feet underwater, unless there's a lot of divers . . . then it can get kind of murky."

Post says that the quarry is open weekends from the last week of March through late fall, and caters exclusively to divers. No boating or fishing is permitted. The entry fee is $7 per person per day; tickets are available at most area dive shops.

"We have an old Piper Cub underwater for divers to investigate," says Post, "and a sunken cabin cruiser and a school bus . . . fun things like that. There's also a 'wall of mirrors' made of up automobile rear-view mirrors for people who like to dive at night. It's quite spectacular."

Russell says there's lots of fish, too, including bass and rainbow trout, along with a few 35-pound catfish that "patrol the quarry like sharks."

The surrounding area is heavily wooded, and geese, beaver, turtles and other types of wildlife are frequent visitors as well.