I don't generally do true black and whites - only one to date - but usually instead add a touch of color, purely for deepening the result. It's not any kind of accuracy that drives the process, only depth.

So, in this case, took about an hour to grope through alternatives (it's the least confident part of my process), until I arrived at a Hue inversion that threw some ochre into the water and some cold blue onto her.

Crazy and counter-intuitive? Somewhat, but I've learned that blue in the shadows is a great asset for form. Ochre in the water? So what. Depth is the point, and all I can do is know it when I see it. (Compare to the previous if you like.)

In an image with a fiery implication anyway, I was happy to play along.