AS BEFITTING A BUNCH of aquatic divers, the Olney Scuba Adventure Dive Club likes to promote the deeper meaning of Christmas. At the Scuba Santa event, now in its fifth year, members collect nonperishable food for the needy, and as a thank you, donors get a mini-scuba lesson and a photo of themselves on Santa's lap underwater at the Olney Swim Center's indoor pool.

"Everybody's in kind of a festive mood around the time of Christmas anyways, but to do something so unique and special . . . when you swim down the length of the pool to see Santa, that's a far cry from braving the crowds at the mall," says club member Joe Lodmell of Silver Spring, a former director of the Scuba Santa event, which is Sunday. In 2004, the club collected more than 1,000 pounds of food for Manna Food Center, a Rockville-based nonprofit group that distributes food to the needy in Montgomery County.

Last year, intrigued by this alternative to the garish setting and gimme-gimme focus of most St. Nick interactions, I took my husband, Matt, and his cousin, Will, then 10, to visit Scuba Santa. I'd never been scuba diving before, and I was excited about this easy way to try it out.

At the pool, we hand over our two grocery bags of canned goods, sign a release form and go to the locker room to change into our suits. We start in the shallow end, and the dive wranglers help me into the backpack-style harness that holds my surprisingly heavy air tank. At their recommendation, I crouch lower in the pool so the water can help support its weight. Much better. But the pink mask that covers my eyes and nose feels like a vise on my head, and I have a hard time trusting the whole you-can-breathe-underwater idea. I chomp on the rubbery mouth-guard-like piece that connects to the tank's air tube and submerge. After a few seconds, I experience my first dive crisis.

I stand up, ripping off the mask and mouthpiece, looking around wildly: "Has anyone seen the 10-year-old who came with me?"

The volunteers do a quick check underwater and reassure me that the lad hasn't drowned. While I've been fussing with my foggy mask, Will and my husband have been cavorting at the other end of the pool, beneath the surface with Santa. Determined, I practice breathing with my mouth just below the water. It works. I sink lower and turn, swimming toward the end of the pool, the club escorts at my side.

Suddenly, it's not that hard anymore. I can see. I can breathe. And -- wow! -- there in the distance, in front of a clear plastic shower curtain printed with fish, is a guy in a white beard and a red, fur-trimmed suit. I forget that I'm wearing all this gear; I feel like I'm in a magical world, like I've spawned superhero powers of built-in gills and laser eyesight. I'm swimming toward Santa Claus! Next to him, the boys wave encouragement.

I swim up to my husband, seated beside Santa on a bench resting on the bottom of the pool. Will's resting on Santa's leg, and next to him is an aluminum tree, complete with a skirt and decked out in tinsel undulating like sea anemone. The volunteers help position me for the photo, and Santa cups my shoulder to keep me from floating away. Down here, there's no way to "ho, ho, ho" or whisper what you want him to bring you; everyone relies on hand gestures to show how jolly we are. The underwater photographer takes a few shots and gives us a thumbs up. Santa releases us, and we wave and make the okay sign to bid him a merry Christmas.

The swim back to the shallow end is even better, because now I've really got the hang of it. I study the blue-tiled lane divider on the bottom of the pool like it's a coral reef. Imagining that there are brightly colored schools of fish swimming next to us instead of the volunteers, I understand how divers get hooked on this euphoria.

Later, I talk on the phone with Cory Briggs, who started the Scuba Santa tradition in 2001 and has since moved to San Diego. He considers diving a way to explore Earth's "inner space," as opposed to outer space, but he likens the mobility of both environments and the unique perspectives they afford.

"You are sort of floating slowly through the medium that surrounds you," Briggs says. "You don't move much faster than an astronaut, and you're not going to have much time to see much of it. You can't stay down very long, so you tend to cherish what little time you do have down there."

The club member who plays Scuba Santa usually stays underwater for most of the afternoon. For maneuverability, the star attraction doesn't wear an air tank, just a mask and a mouthpiece that connects to tanks on the surface via a long hose.

Often two to three members, including women, take turns wearing the red suit.

Harry Arnold of Mount Airy will be Santa for the fourth time this year, so he knows all the tricks of playing the North Pole leader in a liquid habitat. To keep the requisite red hat from floating away, Scuba Santa straps hidden ankle weights around the inside of the brim. Other physics-fighting techniques are less developed, such as how to put a breathing piece on over a fake beard without ending up with a mouthful of synthetic white hair.

Back on the surface and out of our dive gear, Matt and Will check out the center's giant slide at a second pool while we wait for our photos to be printed. The club prints 4-by-6 shots from the digital camera to be picked up the same day or later, or you can request to have the digital pictures emailed to you -- perfect for designing your own holiday card. Poolside, a TV feeds video from underwater so parents can watch their children with Scuba Santa.

The rules of a national certification body -- the Professional Association of Diving Instructors -- don't permit kids younger than 10 to scuba dive. Instead, those 9 and younger can hold their breath and swim down for a quick action shot with Santa, or Santa will go to the concrete steps leading into the pool's shallow end and they can sit on his lap above the surface.

"Water and kids go together," says Scott Hagedorn, the club's president. "Fortunately, some of the 'kids' are well into their twenties and forties and sixties."

SCUBA SANTA -- Sunday noon to 4. Olney Swim Center, 16601 Georgia Ave., Olney. 301-610-4988. A $5 nonperishable food donation is suggested.

Two girls have their photo taken with the big guy at last year's Scuba Santa event at Olney Swim Center's indoor pool.