As an experienced soap maker in real life, I had one of my students nearly do just this. Fortunately, I stopped him in time before he could pour the water into the lye container. And to demonstrate my example. I took a tiny teaspoon of lye, put it in a large metal container, then, using a reaching stick so that we could keep back, poured a small cup of water on top of it.

The hot jetting water, since we were standing back no one got splashed, proved my point a lot more effectively than my scolding.

Lye IN the water, not water over the lye.