Tuna can live 3 to 5 hours out of water.

Tuna are ideally suited for continuous swimming in the open ocean. Their bodies are ideally streamlined in shape, with the thickest part of the body occurring two-fifths of the way back from the head. Their dorsal fin cuts into the grooves to minimize drag, while the caudal fin is stiff and sickle-shaped, providing powerful propulsion. Five to twelve separate small fins behind the anal and second dorsal fins prevent water from forming eddies toward the tail, thus allowing the tail to resist less turbulence. The slender caudal shank has at least two keels that reduce drag and accelerate the flow of water through the tail.

Sports

The tuna family are some of the most active and agile predators. With their sleek, streamlined bodies, the species are also among the fastest swimming pelagic fish. As an example, yellowfin tuna can swim at speeds of up to 75 kilometers per hour. Most tuna are schooling fish, but some can be found individually. They follow a nomadic lifestyle and sometimes migrate long distances. For some groups, migration is seasonal and may be determined by water temperature. Tuna are continuous swimmers, and they have a distinctive, efficient swimming style (known as the fish-tail form), in which the body remains rigid while the long, slender tail swings rapidly.?

Tuna are negatively buoyant and must swim continuously to avoid sinking. In addition, they need constant motion to ventilate their gills. Swimming (at a speed of no less than 65 centimeters per second) forces water to flow over the gills through a process called impaction gill ventilation. Tuna have many lamellae (gill membranes) and very thin lamellar walls that are able to extract more oxygen from the water than any other fish. Tuna have large hearts and blood volumes. They also have a high percentage of red muscle, which allows them to swim continuously, burying themselves along the center of the spine to conserve heat.