A sliver of land 110 miles long and often no more than a mile wide, Eleuthera lies an hour by turboprop southeast of Miami. A few minutes’ drive from North Eleuthera Airport, at the so-called “Glass Window Bridge,” the island narrows to the width of the road. On the Atlantic side, the water is a deep and restless sapphire blue, while to the west, it is a luminous expanse of aquamarine, scarcely disturbed by a ripple. For me, the exquisite and infinitely varied colors of the sea are among the perennial pleasures of the Bahamas.