Swim with whale sharks at the aquarium

Along with the whale sharks, the salt-water exhibit is home to thousands of other animals, including the largest collections of giant grouper, wobbegong sharks and a dozen other rare species.

The dive is far from a free-for-all. During a 15-minute briefing, guides stress a message of conservation and warn participants not to touch any fish while in the tanks. They then don wet suits, snorkels, masks and flippers before plopping into the salty water.

The snorkelers are forced to stay in a rigid line during the swim, kept in toe by dive guides and staffers armed with underwater cameras to document their journey.

It's not a cheap trip, costing $190 for snorkelers and $290 for scuba divers. But the aquarium has so far been encouraged by the response. Aquarium spokesman Dave Santucci said some 1,500 have signed up for the program before its June 8 start.

Krista Massey, an aquarium member who previewed the program, said she felt unnerved when she dipped into the water.

"You know, there's hammerhead sharks in there," she said. "There's all kinds of predators you've been scared of all your life, and all the sudden, you're in their world."

It didn't take long, though, for her to feel more comfortable in the tank — and the experience gave her a deeper sense of wonder for the creatures floating around them.

"What you learn through the process is so much more than what most people know about these animals, and it teaches you a different type of appreciation," she said.

Under the placid surface, too many fish to name swarm below, exotic creatures like zebra sharks, cownose rays and guitar fish. A group of glimmering Golden trevally shimmer around one bend. Not far from there, Grumpy the Grouper, a local icon, glowered near a window.

And of course, there were the four whale sharks, massive beasts that barreled around the tank as they wished, sailing agonizingly close to the awed visitors.

As the 30-minute experience neared its end and the six lined up to depart the cage, the silence underwater was suddenly broken by a warning from a guide.

"Stay flat," she yelled. "Feet up."

Then, a current rippled through the water. And the gentle giant swam by once more.

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