This is really not the focus of our experiments here in Grenoble, but they are too nice not to show: Kelvin-Helmholtz instabilities!
They showed up really nicely in our first experiment, when we only had neutrally-buoyant particles in our source water (and not yet in the ambient water). The water that shows up as the lighter green here is thus water that originally came from the source (and at this point has recirculated out of the canyon again).
I get so fascinated with this kind of things. How can anyone possibly not be interested in fluid dynamics? :-)
Watch the movie below to see them in motion! The scanning works as explained here.