This is one of the rescued sea turtles. What are those round things on his back? Those are weights to help this little guy with his buoyancy. Collision with watercraft can damage their air sacs I believe and leave them unable to swim properly. This guy is little but some can grow enormous! Leatherbacks commonly grow over 1000 pounds. I think the largest one found was over 2000 pounds. If I saw that diving I would be a little nervous.
