As she delivers a bright orange Bahama Mama cocktail that looks like a liquid sunset, the waitress at the Bimini Big Game Club Resort wails: ‘It’s so cold today!’ You could have fooled me. Stretching south-east from Florida, this dazzling sprinkling of 700 islands and 2,400 cays runs for 760 miles, with its highest point, on Cat Island, a mere …