Tagged sharks have been recorded diving to at least 1,928m, well over a mile in depth. That may well be to do with the magnetic navigation mentioned above – deep dives give the sharks a better positional fix – but there’s likely to be some feeding activity at depth, too. The open ocean may be boring at the surface, but there’s plenty going on in the mesopelagic zone a few hundred metres down. Literally trillions of lanternfishes, probably the most abundant vertebrate on the planet, live in this twilight zone. They’d make an excellent snack for a hungry whale shark. Whale sharks prefer surface water temperatures over 21 degrees Celsius. It can be far cooler at depth, with whale sharks occasionally facing near-freezing 2 degrees Celsius. That would be too cold for the sharks to function if they couldn’t retain their body heat. Fortunately, another superlative awaits.