I think that both of those photos use both digital painting and photo manipulation/compositing. I think it would be fairly easy to take a water level photograph and composit it into your scene.
Here are some tutorials digital painting if you’re interested:
http://www.3dtotal.com/team/Tutorials_3/makingof_taishu/taishu_01.asp
http://www.3dtotal.com/team/Tutorials_3/my_world/my_world_01.asp
I’m not sure if you want a quick and easy way to do this - but I played around and I have a way to do this with layer styles and a few brushes. All in all it should take about 10 minutes to create. PM me and I’ll send you the PSD via email. I’ve attached an image for reference.