At a swimming hole north of Baltimore rises a 28-foot-high optical illusion.

Ever since men stopped slicing marble from this quarry in Cockeysville 60-some years ago and filled it with water instead, young swimmers have beheld the diving cliff from below, clambered up the wet stone stairs and been smacked in the face with the deception.

From below: Looks easy.

From above: Isn't.

"It's not that high," said Tiffany Mays, 22, "but it's really far down."

She shivered atop the jumping-off point yesterday, insisting her goose bumps were brought on by the cold, not the terror. But can we be sure?

Her soaked T-shirt read: "You can tell a man's fear by looking in his eyes." Tiffany's eyes are blue, shadow-smudged, and you could tell her fear by looking in them.

Her friend Heidi LaBelle, 17, was having issues, too. "It's kinda scary . . . . It's straight down . . . . I just like the view."

"You go first," prompted Tiffany.

"No, you."

"You!"

So they did it together, as most of the girls do. They held hands and screeched, as most of the girls do.

The boys, on the other hand, muster their bravado silently, take running starts, try to detonate as much splash as possible.

The cliff rings with taunts and swearwords. Supposedly brave teenagers spend 10 minutes urging someone else--anyone else--to go first. They slip back, unnoticed, and try to talk themselves into it.

"It's freaky looking down--very freaky looking down," said Justin House, 12.

Justin is no chicken, no sirree. He didn't look down, just popped out there, arms at his side, a pencil-perfect plunge. "When you hit the water," he said later, "you get this feeling of relief."

That depends on how you land.

With a height nearly three times that of the neighborhood high-dive, there are sore feet (point your toes!), sore chests (don't lean forward!) and wedgies (er, nothing to be done about that) all around.

And when a girl jumps down, down, down into the deep, her bikini top slips up, up, up around her neck. She has only as long as it takes to bubble up to the surface to get it back where it belongs.

But what's burning in the cliff jumpers' brains is not mere boo-boos or indecent exposure, but I'll bust open my head and die.

Malory Wechsler, 14, stood at the edge, lavender fingernails between her teeth. Her freckled face had an I-don't-think-so look.

"Maaal, you're such a wuss!"

"Maaal, come on!"

"Maaal, just go!"

Her pals became distracted and started insulting each other instead. They leapt. Quietly, Malory descended the stone stairs, the way she had come up.

There is a much smaller cliff, and Malory flung herself off that one, in tandem with a friend, and even screeched a little.

CAPTION: Chris Seiler, left, and Josiah Potter, both 16, jump off a cliff in Cockeysville, Md. The deceptively simple-looking 28-foot drop lured many swimmers, and many opted to leap with friends.

CAPTION: Jamie Shrader, 17, watches 16-year-old Kyle Lettau dive at the former marble quarry.

CAPTION: Ross Broton, 14, watches as his friends--Nate Glatfelter, Chris James, Tony Ruth, Kyle Lettau and Chad Lettau--dive off a cliff in Cockeysville, Md.