THE NEXT DAY OUR CLASS meets about a hundred miles inland from Tampa in a dirt parking lot outside the town of Ocala. Across the lot, in the shade of candleberry trees, is a dent in the ground that looks as if it’s been punched by a giant, angry fist. At the bottom of the hole is a pool of bright green water known as the 40 Fathom Grotto. As the name suggests, it plummets down more than 240 feet.
