“We take our shelling very seriously,” said Clark Rambo, on Sanibel Island last month with his wife, Pam, who blogs about the hobby. Specimens pour onto the beach, in part because of the area’s geography.

By Lizette Alvarez, Published August 7, 2012 in the New York Times.

SANIBEL ISLAND, Fla. — The tide is low. The sun crawls toward the ocean for a final dip. The time is here: The hunt is on.

Hundreds take to the beach near the lighthouse on this hammock-shaped island, hunching over the sand as they dig, lift, inspect and move on. The position is so common it has a name: the Sanibel Stoop. The beachcombers wave and chitchat but, with their competitive instincts primed, they steer clear of one another’s turf, keeping a sharp eye out for dots or spirals or telltale lumps in the sand.

“We take our shelling very seriously,” said Clark Rambo, who is known as Super Sheller Clark, a moniker used, sometimes admiringly, sometimes grudgingly, by his wife, Pam. “Every day on the beach is a treasure hunt, and that’s what makes it so competitive.”

Stretched out as far as the eye can see are shells — large, tiny, cone-shaped, scalloped, spiraled, white, orange, pink. Sanibel Island, and its neighbor, Captiva Island, just off the state’s southwest coast, are where hunters come for a seashell bonanza. There is no other place like it in the country, and very few places like it in the world. On some days, depending on the wind, shells pour onto the beach in piles, seducing even the most jaded beachgoers.

This has been particularly true in the weeks since Tropical Storm Debby, the late June storm that caused flooding and beach erosion along some pockets of Florida’s west coast but proved a boon to seashell hunters.

A sampling of the shells

Sanibel’s largess is in its geometry: It is a 12-mile barrier island with a distinctive curve. The coastline runs west to east rather than north to south. When storms blow in from the northwest, the waves and currents funnel more than 300 shallow-water species of shells right onto the beach. Other parts of the world, like the South Pacific, may draw more species, but the shells are not nearly as easy to find. They require boat trips and dives.

“There are days here when you have layers of shells four feet thick,” said José H. Leal, the director of the Bailey-Matthews Shell Museum here. “It’s one of the best places in the world for shelling, for sure.”

Seashells have proved resilient, too. At a time when fish stocks are down and coral reefs are dying, Mr. Leal said seashells — made by mollusks mostly from the calcium carbonate in seawater — continue to thrive.

For some, searching for seashells is a hobby; for others, it is a calling and an obsession that sometimes reaches back generations, with collections passed down like heirlooms. Here, there are shell clubs, shell stores, shell guides, shell excursions, shell crafts and the shell museum.

Inside his shell-festooned house, Mr. Rambo holds dear a black-and-white photo of his room as a boy. The image shows his twin bed, spread with seashells mostly scooped from the Jersey Shore. Mrs. Rambo, an artist, also grew up collecting shells, a shared passion that helped cement the couple’s relationship 18 years ago, despite Mr. Rambo’s being injured during a date.

It happened during a day of shelling on Sanibel early in the courtship; she pushed him (playfully) as he stood, his feet dug into the wet sand.

“My leg did a spiral twist,” he said. “Sounded like a shotgun.”

Now Mrs. Rambo is a sought-after figure on the island — a shell-ebrity, if you will — because of her popular Web site, www.iloveshelling.com. It is routine for her to be stopped to listen to a fan rattle off a list of finds (tulips, conchs, whelks, murex) or to answer a question about where to go and when. (The answer is Lighthouse Beach and Blind Pass, which lies between Sanibel and Captiva at low tide, when the wind is westerly, preferably after a storm.)

On a recent evening, shell hunters hungrily swept the beach with their eyes. They picked up shells and peered inside them.

“Is anybody home in there?” Mrs. Rambo asked. If a mollusk was inside, she placed the shell back on the sand. That is the rule in these parts — no live shelling. Before a 1994 law, people hauled boxes of shells away and began depleting the shoreline.

In front of the lighthouse, a teenage boy picked up a starfish and showed it off. A woman from North Carolina dug a hole. She recognized Mrs. Rambo. “I’ve probably found 15 bittersweets,” Denise Kisko, 56, told her, referring to a scallop-shaped shell. She glanced at a 13-year-old girl who was snooping in her spot. “Don’t you find anything in my pile,” she said, kidding, sort of.

Competition is stiff. The morning last October that Mrs. Rambo found a precious, elusive junonia, a species of sea snail known for its brown spots, she had told friends to meet her at Blind Pass at sunrise. Hoping to beat the competition, she got there before sunrise, with a light on her hat, to hunt solo. She spotted the junonia in a little trench. It was her eureka moment.

“I started screaming,” she said. “I was a shellunatic.”

Never mind that her husband has found four junonia over his lifetime, a remarkable feat he loves to sprinkle into conversations. After he posted a photo of his fourth junonia online, it proved too much for the shell crowd.

“They started booing him on the Web site,” Mrs. Rambo said, with a laugh.