A man walks at sunset down Bowman's Beach on Sanibel Island, Florida.

For a beach lover, the beaches of Fort Myers and Sanibel are a dream destination.

Trouble in paradise: I’m at the tollbooth on the causeway that crosses to Sanibel Island from Fort Myers, Florida. There’s a six-dollar charge, and they don’t take credit cards. After fumbling through pockets, purse, and beach bag, I come up with only four crumpled one-dollar bills. But the tan booth attendant offers an authentic smile. “If you don’t have it, it’s OK,” she says, waving me through. “Someone ahead of you just paid it forward.”

Receiving a favor from a stranger is an unexpected welcome to the islands west of Fort Myers. But it’s just one of many things that make the area unusual.

The barrier islands are off of the mainland and have wide inlets from the Gulf of Mexico that are fed by several rivers. The largest, the Caloosahatchee River, provided transportation far inland for the Calusa people long before the Spanish explorers came, and it’s still popular for boaters. But these days most travelers arrive in Fort Myers via Interstate 75 or at Southwest Florida International Airport, drawn by the beaches, wildlife, and—especially—shells.