Actually I don't think the split is well done. It looks like someone used Photoshop to change the color balance of a rectangle region.

The fishes don't seem right in their sizes (exspecially the small fishes seem far too big).

There are tiny waves on the water surface. These should be taken into considerance at the split line, which should follow the surface of the water (being a bit wavy).

Although the fishes "down below" have shadows I am mising the shadows of the boat and the wood. I am not sure, but I think the lighting isn't correct as well (there are reflections on the ground which somehow should be visible on the water surface as well).