You can ride Sea Turtles in the same manner as a pig.
They move extremely slowly on land, but a bit faster in water. You can control the direction the turtle will swim when riding it, but not tell it to surface. Turtles have 25 hearts (50 points) of health, which can be seen while riding it. If you kill it, it will drop a Turtle Shell.
Sea turtles can be hatched from eggs found near adult sea turtles. To hatch, place the eggs on land near a body of water. The eggs should only take a few seconds to hatch and will start rocking back and forth. When the baby turtle hatches out, it will find the nearest body of water by itself.