My heart races as I turn this way and that, sucking air through a hose, peering through a mask, intently following its progress.

Upward the shark swims, slowly, warily, casting a vacant gaze through ominous black eyes. Dagger-like teeth protrude from its lower jaw.

Forty feet . . . 30 . . .

This colossal specimen, 16 feet long and 2,000 pounds, could sever a man with little effort.

Yet its movements are surprisingly cautious. It's as if thousands of years of evolution have taught it to leave nothing to chance, to give thorough inspection.

I'm behind the bars of a submerged steel cage, but it has gaps wide enough to swim through and I keep leaning out to gain an unobstructed view, then jerking back because of fear and paranoia.

Twenty feet . . . 10 . . .

Anxiety builds until, for some reason, it becomes exhilaration. I'm overwhelmed with desire to film this remarkable creature.

So again I reach out and hold my camera steady, as the shark glides closer and closer still, until its menacing face fills my monitor and I glance up to discover that this great predator is only a few feet away.

Our eyes meet and I pitch back inside, startled to my senses, stumbling under the heft of my weighted harness. Cindy Rhodes, my cage partner, has also fallen back. We glance bug-eyed at each other while trying to regain our composure.

Back aboard the ship we'll learn that ours is a common reflex -- although divers are told to keep all limbs inside -- and that our clumsy waltz even has a catchy title: the "White Shark Shuffle."

It's performed frequently each summer and fall in the strikingly blue water flanking the eastern shore of Guadalupe Island, a 22-mile-long volcanic land mass about 150 miles west of Baja California.

Guadalupe emerged in the last five years as perhaps the world's premier destination for diving with especially large great white sharks, and with such distinction has come controversy and concern.

Competition is fierce among the five commercial outfitters permitted to dive here. Regulations are strict but almost impossible to enforce because the Mexican park service cannot afford to police so far-flung a destination.

Thus, outfitters are wary of one another and rumors swirl regarding this boat or that, about questionable chumming tactics -- and risking of lives.

"If you don't play by the rules, you make life difficult for the park service and place all of this in jeopardy," says Mike Lever, captain of the Canada-flagged Nautilus Explorer, who will not point fingers. "We need to stand together in order to make this industry sustainable."

Outfitters charge up to $3,000 per person for a five-day excursion, which includes three days of diving.

White shark seekers, whose only viable options are South Africa or Australia, consider a Guadalupe voyage extreme adventure, a chance to face fears and bond with others while becoming intimate with the ocean's most notorious, yet misunderstood, predator.