Depending on the species, a turtle can stay under water for hours, days, weeks or even months. During hibernation, painted turtles remain underwater through the entire winter. Turtles that spend large amounts of time submerged have developed specialized means of capturing oxygen from the surrounding water via gills, special cells or their skin.
Some turtles that need to surface in order to take in oxygen have been known to hold their breath for considerably long amounts of time. For example, the Leatherback sea turtle can hold its breath for up to 7 hours at a time. On the other hand, the common musk turtle has eliminated its need to resurface by developing special cells on its tongue called papillae that allow it to separate oxygen from the water while the turtle is submerged.
The National Oceanic and Atmospheric Administration states that sea turtles can stay underwater for two hours without breathing. This assumes the animal is at rest and not active. When active, a sea turtle must return to the ocean's surface every few minutes. The leatherback sea turtle is the largest of all turtles, capable of reaching a length of 6 feet and weighing 1,400 pounds.