These Hammerhead Sharks Are the First Fish Known to Hold Their Breath Underwater

Scalloped hammerheads can close their gills on deep dives. This stops them from losing valuable body heat as they hunt. Most fish are cold-blooded and depend on the surrounding water to keep warm. And because gills are full of blood fish lose body heat through them very quickly. Scalloped hammerheads spend most of their time in warm waters. But they hunt at depths of around 800 metres, in temperatures as low as 5˚C and to hunt effectively, they need to keep warm.