Crunch, crunch, crunch.

With each step I took, scads of seashells beneath my feet were at risk of being crushed. There was no way to avoid the danger to the shells.

I was on Sanibel Island, Florida, the unofficial seashell capital of the United States, and great swaths of seashells — hundreds of different kinds — covered the beach, from the crystal clear Gulf of Mexico waterline to the highest tide line.

I had traveled with my wife, a self-proclaimed seashell aficionado, to Sanibel to check out the island’s bounty before the third annual Island Hopper Songwriter Fest from Sept. 23 to Oct. 2.

Fall is the perfect time for a visit to Sanibel, one of three barrier islands off the coast at Fort Myers (the others are Captiva Island and Estero Island, which is occupied by the resort town of Fort Myers Beach). Kids are back in school, and northern “snowbirds” (vacationers and winter residents) don’t start arriving until early November.

Hotels offer rooms at steep discounts. And, for the third year in a row, dozens of singer-songwriters will entertain visitors with free performances at bars, restaurants and outdoor spaces on the islands and in downtown Fort Myers (which is worth a visit in its own right for tours of the winter homes of Thomas Alva Edison and Henry Ford).

This wasn’t our first visit to Sanibel. We had been there several times already. But, following reports of a storm a week earlier, we decided a visit to the island was in order.

Storms wash up the shells in vast quantities on Sanibel because of the island’s geography — it juts out into the Gulf in a hook shape, its beaches catching the shells that are pushed ahead of the storm surge. The Gulf’s prevailing currents and each day’s tides also deposit shells.

But a warning: Those visiting for the first time often expect to find treasures akin to the great pink and orange conchs and other huge shells found in the warmer Caribbean Sea.

The colorful Florida fighting conch isn’t as big as its Caribbean relatives, but it’s just as colorful; most of Sanibel’s shells are smaller, though no less exotic, than their warm-water counterparts elsewhere.

The shells found on Sanibel’s beaches include huge numbers of whelks, which look like smaller, elongated conchs; a universe of scallop shells of all colors; and tulip shells, calico clams, giant heart cockles, king’s crowns, common jingles, cat’s paws, shark eyes, nutmegs, Atlantic figs and horse conchs (the official state shell of Florida), just to name a few of the hundreds of species that wash up on the island’s beaches.

There are also cone shells, some of which sting with a sharp extendable harpoon, sometimes causing paralysis and, in the time that somewhat-accurate records have been kept, 30 deaths (none of them in the United States).

We opted to take one of the daily beach walks offered by a marine biologist from the Bailey-Matthews National Shell Museum, located on Sanibel, which lies off the southwest coast of Florida across a 6-mile-long causeway from the city of Fort Myers.

Our guide was Stefanie Wolf, a young woman from Green Bay, Wisconsin, who had studied ecology for her undergraduate degree and continued on to a master’s degree in biology. She started by reviewing the ground rules for the walk.

The shells, she said, were merely the hard, protective exoskeletons of the animals that lived inside them. And, while many of the shells that visitors find are empty husks, others are still living.

To determine whether they’re alive, she said, you look into the shell’s opening; if it’s occluded with a firm membrane or if the shells of bivalves are tightly clasped, the shell is living.

Living ones should be placed back in the water — gently. With a look of disdain, the otherwise dispassionate Wolf told the group about one person on a beach walk who threw a living shell back into the water.

“They’re living animals, for God’s sake,” she said. “Treat them with respect; don’t football them.”

Wolf imparted one last rule: It’s illegal to take living shells out of Lee County, in which Sanibel Island is located. The message was clear: Don’t let the law — or her — catch you absconding with them.

For the next hour, we walked along the beach as Wolf, wearing glamorous sunglasses, picked up shells she found at the water line and talked about them.

One thing quickly became clear: Wolf really knew her stuff, as had Marine Biologist Rebecca Mensch, a young expert on squid (with squid tattoos) with whom we had taken the shell walk a year earlier.

In terms that were occasionally more scientific than some members of our small group might have liked — I’m raising my hand here — Wolf told us all about each shell she proffered.

Much of Wolf’s focus was on the reproductive habits of mollusks, the correct name for the animals inhabiting the shells, although she also dwelled on their eating habits, as many of the creatures are carnivores, not herbivores. (The previously mentioned Florida fighting conch, she told us, is a herbivore and gets along fine with other mollusks despite its name.)

When they’re ready to lay eggs, whelks, for example, produce voluminous strands of sponge-like egg cases, which we found frequently on our tour. Eggs are deposited into tiny apertures, from which they emerge as juveniles.

As for the carnivores, the meat eaters of the shell world, several, including the nauticas and shark eyes, latch laterally onto the shell of their intended victim, then use a sharp protuberance to drill a hole into the animal inside the shell, killing it. It takes just a few hours, and dinner soon follows.

The price of our beach tour, $10, included a 50-percent discount to the Bailey-Matthews National Shell Museum on the other side of the island, closer to the mainland and across the road from the main entrance to the J.N. Ding Darling National Wildlife Refuge, maintained by the U.S. Fish and Wildlife Service, which also draws large numbers of visitors to Sanibel Island.

Near the museum’s entrance, a plaque dedicated to Raymond Burr expressed gratitude for support of the museum’s founding in 1995.

I asked Alec Economakis, the engaging college student from Potomac, Maryland, at the ticket podium, if the Raymond Burr on the plaque was the actor who starred in the old “Perry Mason” and “Ironside” TV shows. He replied in the affirmative, taking the opportunity to talk about the museum’s history and collection.

Burr, a part-time resident of both neighboring Captiva Island and Fiji, liked to collect shells as well as catch TV criminals. His vast collection included many rare species, and, when invited to help fund the new museum, he apparently leapt at the opportunity.

We opted to take in the tank show, a featured attraction; it was led by Wolf, and covered much of the same ground as our beach tour. (The terminology seemed even more scientific; this might not be the best event for young children.)

One large tank was populated by shells that might co-exist in the ocean — both herbivores and carnivores.

“Some mornings, when we come to work, we notice that some of the mollusks are missing,” Wolf told her audience. “They sometimes eat each other overnight.”

We had never guessed that the life of a seashell could be fraught with such peril.

Martin W.G. King is a freelance writer based in Delray Beach, Florida.

The 2016 Island Hopper Songwriter Fest goes from Sept. 23 to Oct. 2. It starts on Captiva Island, which is connected to Sanibel Island by a causeway, with performances Sept. 23-25; continues with midweek performances in lively downtown Fort Myers; and ends Oct. 2 in Fort Myers Beach on Estero Island.

The headline act this year is Maren Morris, whose country hit “My Church” is rising on the Billboard Hot Country chart.

For more information on the lineup and festival venues, call 239-454-7500 or go to www.fortmyers-sanibel.com/island-hopper.

Sanibel Island has excellent beaches with clean restroom facilities and metered public parking (which gets scarce in high season). Bathers sometimes share the warm waters with dolphins, which often swim close to shore. Bowman Beach (mid-island) and Lighthouse Beach (closest to the causeway from the mainland) are among the most popular choices.

Well-marked off-road bike paths line Sanibel Island’s main thoroughfares, particularly Periwinkle Way, where you can ride for miles. Billy’s Rentals is one of several outfits that rents single-speed and high-performance road bikes and scooters.

Billy’s is at 1470 Periwinkle Way; 239-472-5248, www.billysrentals.com/bikes/.

More Information on Sanibel sightseeing and shelling trips: sanibel-island.sanibel-captiva.org. In addition, the Sanibel and Captiva Island Chamber of Commerce’s visitor information center is at 1159 Causeway Road on Sanibel Island, 239-472-1080, https://sanibel-captiva.org/.

n Daily Island Beach Walk

$10 adults, $7 children (includes half off admission to the Bailey-Matthews National Seashell Museum)

Leaves from Island Inn, 3111 West Gulf Drive, 9 a.m.

Reservations essential: purchase tickets online or call 239-395-2233.

n Bailey-Matthews National Shell Museum

3075 Sanibel-Captiva Road, Sanibel Island, 10 a.m. to 5 p.m.

Daily museum talks; topics vary by day of week.

239-395-2233, www.shellmuseum.org/.

$11 adults, Children 5-17 years old, $5

n J.N. “Ding” Darling National Wildlife Reserve (National Fish and Wildlife Service)

Two miles west of Tarpon Bay Road on Sanibel-Captiva Road, Sanibel Island, 9 a.m. to 5 p.m. January to April, and 9 a.m. to 4p.m. May to December.

Drive a marked route through alligator and bird habitats, $5 per car; $1 per biker or hiker.

Education center with exhibits on refuge ecosystems, migratory flyways, daily talks and a bookstore.

Popular tram tour, narrated, $13 adults, $8 children; reservations and availability (times vary by day of week), 239-472-8900 or concessionaire Tarpon Bay Explorers website for information, tarponbayexplorers.com/tour/refuge-tram-tour/.

Tarpon Bay Explorers also offers guided kayak trips, kayak rentals and a nature cruise, with some of the proceeds benefiting the Fish and Wildlife Service. For times and prices, call 239-472-8900, or go to tarponbayexplorers.com/.

(Main “Ding” Darling website: https://fws.gov/dingdarling/visitorinformation.html)

n Very expensive: Il Cielo

Italian cuisine with live piano each night.

1244 Periwinkle Way, 239-472-5555, www.ilcielosanibel.com/.

n Expensive: Sweet Melissa’s Café

Well-regarded innovative cuisine.

1625 Periwinkle Way, 239-472-1956, sweetmelissascafe.com/.

n Moderate: The Sandbar

Superb steaks and fish dishes at reasonable prices in pleasant surroundings; excellent, friendly service.

2761 West Gulf Drive, 239-472-0305, www.sanibelsandbar.com/.

n Moderate: The Mucky Duck

A local institution on Captiva Island reminiscent of a neighborhood pub, but at higher prices.

11546 Andy Rosse Lane, 239-472-3434, www.muckyduck.com/.

n Inexpensive to moderate: The Lazy Flamingo

Fish, shellfish and burgers; happy hour (beer and wine only) each night 9:30 p.m. to midnight; one of the few places on Sanibel Island open late.

1036 Periwinkle Way, 239-472-6939, www.lazyflamingo.com/.

n Inexpensive: Over Easy Café

Breakfast and lunch until 3 p.m.; a local institution that’s always crowded; closed Sept. 12-22

630 Tarpon Bay Road, 239-472-2625, www.overeasycafesanibel.com/.

n Inexpensive: Island Cow

Usually a wait in line for good, cheap eats at breakfast, lunch and dinner.

2163 Periwinkle Way, 239-472-0606, sanibelislandcow.com/.

n Casa Ybel Resort

Large, full-service, Sanibel Island beachside resort with all amenities, from $291.

2255 W. Gulf Drive, 800-276-4753, www.casaybelresort.com/.

n Song of the Sea

Small boutique hotel on the Sanibel Island beach, from $151.

863 E. Gulf Drive, 239-472-5170, www.theinnsofsanibel.com/song-of-the-sea/.

n Sundial Beach Resort and Spa Large resort with landscaped grounds directly on the beach on Sanibel Island, from $142.

1451 Middle Gulf Drive, 239-472-4151, www.sundialresort.com/.

n Pierview Hotel and Suites

Modern rooms on the beach in the resort town of Fort Myers Beach, from $130.

1160 Estero Blvd., 239-463-6158, www.pierviewhotelfmb.com/.

n Seaside Inn

Pleasant rooms and cottages around a pool, on a Sanibel Island beach, from $124.

541 E. Gulf Drive, 239-472-1400, www.theinnsofsanibel.com/seaside-inn.

n Captiva Island Inn

Charming bed and breakfast 150 yards to the beach, rooms and cottages from $119.

11508 Andy Rosse Lane, Captiva Island, 239-395-0882, captivaislandinn.com/.

n Hotel Indigo

Stylish if small rooms on the edge of the Fort Myers River District, the city’s lively downtown; rooftop pool and lounge, from $115.

1520 Broadway, Fort Myers, 239-337-3446, www.ihg.com/hotelindigo.

n La Quinta Fort Myers-Sanibel Gateway

Chain lodgings close to the causeway from Fort Myers to Sanibel Island, rooms from $66.

20091 Summerlin Road, Fort Myers, 239-466-1200, www.laquintafortmyersbeachsanibel.com/.