They use their forelimbs as flippers to propel them through the water. The average swimming speed for a sea turtle is about 0.9-1.4 mph. Although, Leatherback sea turtles have been recorded at 0.9-5.8 mph. Unlike land turtles, sea turtles' neck and limbs cannot be retracted under their shell. If they were able to pull them into their shells, sea turtles wouldn't be as fast of swimmers.
Sea turtles are also great divers.
Leatherbacks average 1,000 feet on dives, and can reach depths of 3,900 feet to capture jellyfish. Sea turtles have a very slow metabolic rate, allowing them to be under water for long periods of time. A Green sea turtles' heart beats once every 9 minutes to conserve oxygen. This gives them enough oxygen to stay under water for up to five hours. Eating Habits Different species of turtles, eat different foods.