Every April and May some of the largest animals on earth, whale sharks, congregate in their hundreds at Ningaloo Reef, off Australia’s West Coast. Exactly where they come from and where they go from here remains a mystery.

Ian Gordon sets out to help Dr John Stevens, of Australia’s CSIRO (Commonwealth Scientific and Industrial Research Organisation), to track these huge creatures successfully by attaching a secure transmitter to their fins.

With help from experienced Australian whale shark diver Peter Lake, Ian has just two weeks to accomplish the mission before the sharks begin to disperse. Although known as the “gentle giants” of the ocean these animals could seriously injure a diver with a flick of their powerful tail.

“Sharkbite”, a 30-foot (9.2 metre) male, is successfully tagged. But things take a turn for the worse when Sharkbite manages to dislodge the expensive tag and 30 knot winds plague the mission for several days.

A second tag arrives with just one day to spare and an exhausting chase ensues.