NAPLES, Fla. — Most people from the Northeast move to Florida to get out of the cold. Colleen Gill came to Naples because she heard the call of the wild.

She had vacationed on this slice of coastal paradise for 20 years. She made regular jaunts to the Big Cypress National Preserve, home to cypress swamps and wild panthers. She kayaked in the Gulf. With each visit, she fell more in love.

Ms. Gill and her husband own a hemp footwear company that they can manage from anywhere. So they sold their house in New Hampshire three years ago and headed down for good.

Ms. Gill, 38, coveted her regular long walks on the white-sand beaches. By last summer, the walks had turned gruesome. Increasingly, there would be eels, tarpon and sea turtles dead or dying along the tide line.