Painting water always looks so daunting at first. I've found that calm waters are actually a blast to paint if it is done in order....it just looks daunting when you view it complete. Some artists will paint it totally different but this is just my method. What I do is break down the colors to the "Base" colors and then the colors that will overlap those Base colors. Lastly, I will paint in specks of white as the suns brightest reflections. Above I have began to block in some dark shadows along the hull and started adding my initial Base colors.
Below, I finish up the base colors, the cool grey and the warmer grey as well as the sky reflections and shed colors. If you look at calm waters you will see these base colors...you need to paint these first and then add all of your detail colors overplapping them. This method is just an orderly way of painting water that at first may look confusing to an artist. It's just a matter of breaking the parts down and assigning some priority.
Now the details are added. This has to be the most fun step of painting water. You use what you see as a reference and please remember that your photo or actual location image is only a reference...you can get as creative as you want and there is no need to paint every single detail or paint these details just as they are in front of you or in your ref photo. I've left some things out, added some things, changed colors to what I wanted or embellished what colors were there....it's my painting anyways.
I'm still working on this painting so nothing here is concrete. As soon as these colors a dry enough I'll add my white specks of "sunlight" reflections to give it some sparkle. I think it is all headed in the right direction though and I'm getting close to calling it done...a day or two still.
So, that's it. Paint in the base colors, add detail colors and then a few white (or close to white) highlights to finish it up. This is a method that works for me....give it a try sometime and see what you come up with.