First he hears a faint chatter coming from the ocean depths, then clicks and squeaks as the creatures draw closer. From the murky edges of his goggles they appear, swift and agile, darting within 10cm of his bare outstretched arms and following him for a time, as he swims hundreds of metres off the coast of New Zealand.
Jono Ridler, an ultra-distance swimmer who is 1,254km (779 miles) into his world record attempt for the longest-ever unassisted staged swim, has learned to hear dolphins more than 15 minutes before they reach him and long before his support boats can see them.
