After you breed turtles, one of them goes off in search of the beach, but after a little bit it simply freezes in the water. You can push them around, but they don't move or swim on their own. It's only the female that does this. I reloaded the game and the problem persists. You can injure the turtle and it will move for about 10-20 seconds before freezing again. This is a really annoying bug, especially when you are trying to start a turtle farm.