Tuna is a saltwater predator. There are 15 types of Tuna, ranging in size from 50 cm to 4.6 m and weighing up to 684 kg (bluefin Tuna). It’s one of the few species that can maintain their body temperature higher than that of the water they swim in. Their hydrodynamic bodies make Tuna enviably fast. Tuna found in the Adriatic Sea can weigh from 30 to 200 kg or more.