The slowest turtle is said to move at a speed of 0.23 miles per hour while the fastest can reach up to 15 miles per hour. it is a huge difference. in water, the quickest turtle can move at 22 miles per hour. away from the fastest or slowest turtles, generally, turtles will walk at a speed of about 3 to 4 miles per hour and swim at about 10 to 12 miles per hour.