Just expanded upon: Photoshop Landscape Painting article with tons of new helpful tutorials on how to paint the Sea, Lakes, Oceans, and other bodies of water. A little more on the art of Mountain Painting in Photoshop. This is becoming a big resource on the topic and it keeps expanding for you. Free, useful info.
Includes step by step instructions (unlike many tutorials). I forsee a Video Tutorial connected to this in the future, but no time right now. Click here to go to the Article.