Some time in December, Ben Hooper will step on to a beach in Dakar, Senegal, and plunge into the warm blue waters of the Atlantic. He will not stop swimming until he hits Natal in Brazil. The distance is 1,763 miles. But that’s only if he goes in a straight line. And swimming across the Atlantic in a straight line is a bad idea: “The currents in the centre are so strong, I’d never get there. It’s an absolute car wreck in the centre. Great for rowers, great for sailors, horrible for swimmers,” he says. Instead he will go in...