I was kneeling under 12 feet of water when the sensation began, the feeling of something soft and velvety on the back of my neck. A minute passed, then another, and it was still there, a feathery pressure.
There were nine sharks, including two very playful zebra sharks, swimming near me, but I wasn't worried about the tickle coming from one of them. They all kept a respectable - if not respectful - distance, even if that was barely a foot away at times. After all, I had told dive master Yves Delpech I would not be intimidated by having the creatures on top of me, in a manner of speaking.
But when I decided to reach back and brush away what I felt on my neck, Yves, who was behind me, suddenly pushed my hand.
"Didn't want you to put your hand in Gill's mouth," he said after we finished the dive.
Gill is a 250-pound Goliath grouper who finds great sport in perching on the head or shoulders of folks whose attention is on the toothy critters who are the prime attractions in the "Dive With the Sharks" program at the Florida Aquarium in downtown Tampa. He also has several rows of teeth sharp enough to seize the crustaceans that are part of this grouper species' normal diet.
The big grouper goofs with visitors as relentlessly as the blind zebra shark, Zoe, who lives in the Wings in the Water tank of the National Aquarium in Baltimore, another of several aquariums in the country that offer qualified patrons the chance to pay for a dive with some exotic critters.
Zoe kept bumping me and rubbing against me, the abrasive quality of her skin evident despite my 3-millimeter-thick wetsuit. She wanted some of the food I was feeding the 36 rays in the Wings tank, assisting the aquarium's volunteer divers.
The feeding isn't part of the guest-diver program in Baltimore, where I was encouraged to stick a hand (full of squid) into a ray's mouth. But the animals remain "interactive": Rays brush their silky undersides across the guest divers' heads, and Zoe leans on them like a border collie herding sheep. The experience provides plenty of fun to divers feeling starved for the pleasure of plunging into warm-water environments. There are also hours of "dry" diversions in the multiple galleries at each aquarium.
Baltimore and Tampa's programs, which I experienced this spring, and similar ones are open to certified divers, but age minimums, certification requirements and the equipment provided vary. Check the aquariums' Web sites for more information.
(The program at the Georgia Aquarium in Atlanta has been questioned by some marine experts who fear whale sharks at the aquarium may suffer adverse effects.)
Why dive in an aquarium when there are oceans and lakes aplenty?
The cost is far less than a trip to Hawaii or Belize or the Caymans, to name a few popular dive destinations I have visited. If you live near one of these aquariums, the experience can be part of a fun staycation. If you don't live near one, you can pair a dive with a trip to a major city, and your kids (if they are too young to dive) can have a ball in the aquarium and watch through "underwater" windows as their family members frolic with the fish. Also, all learn something about the threats facing our marine habitats.
Did I mention water temperature? Tropical is my cup of sea, and that is what I got (about 75 degrees) in Baltimore and Tampa.
On top of that, the aquariums' biggest tanks are so relatively shallow that air consumption is no issue, even for "heavy breathers" like me. You won't run out of air - or things to see.
"You would need 25 years of diving to interact with as many species as you do on these two 30-minute dives," said John Harman of Atlantic Edge Dive Center, which runs the guest diver program for the Baltimore aquarium. "We have one woman who has done this dive five times."
The biweekly Baltimore program ($295) offers 12 divers a chance to explore the aquarium's 13-foot-deep artificial Atlantic Coral Reef - with tube and fern coral and other fauna rendered in stunningly real detail - and its 9-foot-deep ray tank. (Anyone who has dived Stingray City off Grand Cayman will know how enjoyable it is to encounter the rays in shallow water.)
The circular coral reef has 60 species of fish, including some spectacularly large angels, several types of grouper (all much smaller than Tampa's Gill), wrasses, margates, snapper and a green moray eel named Oscar. You can glide under archways, squeeze through a "cave" and swim at different levels.
The six types of rays and Zoe the zebra shark have been sharing the Wings in the Water tank with Atlantic tarpon, a blacknose shark and Calypso the green sea turtle.
I got to scratch Calypso's back, which causes a similar reaction to scratching a dog's "magic spot."
You will learn about the aquarium's Marine Animal Rescue Program and its volunteer diver program during the 60-minute dive briefing Atlantic Edge gives.
In his shark-dive briefing, Tampa aquarium dive master Mike Knudsen dispelled some myths about sharks. These much-feared creatures need better press agents because they don't get much good publicity. (What do you ever hear about a shark until one attacks a person who often is doing something foolhardy, such as swimming in a wet suit in areas with known shark inhabitants? They think the human looks like a tasty seal.)
Shark populations are dropping worldwide because of demand for their fins (shark fin soup is an Asian delicacy), their meat, teeth and hides. They do not reproduce fast enough to keep up with the numbers being fished out of the seas.
Tampa has five types of sharks, none of them "man-eaters" (Great white, tiger and bull are the only truly dangerous species, Knudsen said). The two nurse sharks lay on the sand during my 30 minutes in the tank, debunking the idea that sharks always move.
After exiting the cage used to descend into Shark Bay, the guest diver swims to a spot and then also is passive in this program, kneeling on the bottom and holding a large rock to avoid significant movement. The tank's confines are so limited that the sharks, the grouper and a hawksbill sea turtle are almost always at close range as they move.
The zebras did underwater loop the loops, a display that seemed purposefully comical. The steely gray sand tigers glided lazily around me, seemingly staring with their eerily bright eyes and revealing the rows of impressive teeth they constantly shed.
Florida Aquarium officials note that from the time the facility opened in March 1995 through April of this year, volunteer, staff and guest divers have spent more than 44,300 hours diving and completed 49,500 dives, and there have been zero shark incidents.
There was one unnerving moment, when a sound like an exploding cannon echoed through the water. That was just Gill, venting the air in his swim bladder. Fortunately, he swam away from my head before doing this whoopee cushion act.
Philip Hersh writes for the Chicago Tribune.
If you go
Some U.S. aquariums that offer guest-diver programs:
Georgia Aquarium, Atlanta. Journey With Gentle Giants (a whale shark, the world's largest fish, is the prime attraction). One 30-minute dive. Daily ($290). Go to georgiaaquarium .org/swimordive/index.aspx.
Florida Aquarium, Tampa. Dive With the Sharks. One 30-minute dive. Daily ($150). Go to flaquarium.org.
National Aquarium in Baltimore. Dive the Wings in the Water and Atlantic Coral Reef tanks. One 30-minute dive in each tank ($295). Every other Saturday. Go to aqua.org.
Adventure Aquarium , Camden, N.J. Sharks Up-Close, Thursdays and Saturdays, Memorial Day through Labor Day; Saturdays all other times. Sea Life Up-Close, Fridays and Sundays, Memorial Day through Labor Day; Sundays all other times ($195 for either). Go to adventureaquarium.com
Epcot Center, Orlando, Fla. Epcot Dive Quest, sharks, eagle rays, sea turtles, plus more than 60 fish species. Forty-minute dive ($150). Twice daily. Go to epcotdivequest.com