Continuity mistake: When Leo and his group of rebel apes are starting to ride their horses across the river, the Bonham-Carter character falls off her horse and he swims across the river with her on his back. The other apes can't follow because they're afraid of water. So they arrive horseless. However, when they get across the river, suddenly everybody has horses.
Continuity mistake: When Leo dives in the pond where his pod crashed, to get his bag, it is dark and dingy, yet when you see an underwater shot the water is a clear blue/green colour and you can see the sun (or some form of light) shining through the water, yet when he comes out there is no light and it is dingy again.