OK. Embarrassment time, but I've always wanted to ask this.
You say "white balance on the water" but there's no white on the water. So HOW? It looks GREAT, but I don't have a clue what setting you used, or more importantly, WHY!
WB is based on 80% (or something like that) gray? Or am I in over my head?
I think you're thinking of 18% grey which is the reference brightness that simple auto exposure is based upon.
Basically, the camera *assumes* that every scene is an average scene and an average scene is assumed to be one that looks good when exposed to reproduce 18% grey subject as 18% grey in the output. If your subject is far from average (white cat in snow or black cat on a dark background), then exposure will be off--unless the user compensates.
The autoexposure system assumes that 'all cats are grey'. So the white cat on snow will turn out a muddy (18%) grey if you don't compensate. Since you 'know' the cat and snow are white, you know that more light needs to get to the sensor for proper exposure. In our flying cameras the lens aperture is fixed so you either decrease shutter speed or increase sensitivity (ISO). Some systems also allow an EV (exposure value) adjustment which accomplishes the same thing. With an appropriate exposure adjustment, your white cat on snow looks white.
While small image adjustments to an improperly exposed original can be made, it's best to capture photos or video at the correct exposure from the start. This is all basic photography/videography (i.e. has nothing to do with flying cameras) so any basic photo or video tutorial will cover these concepts.