Originally posted by HomeMadeSin Thanks for the input! In my limited photo aptitude, I chose a fast lens (50mm 1.4 if I recall correctly) to allow as much light as I could with short duration, intending to get as much stop action. I realize the plastic reflection, distance between the two plastic surfaces (upper and lower), "thickness" of the water stream, etc would be a challenge. I just did not get the stop action I was seeking. For reference, I was using a 500 watt spotlight (the ones that get really hot) to generate some light to help shorten the exposure time. So hopefully, you can see the "primitive logic" I used including high ISO.
One thing you can try is simply use the pop-up flash on your camera.
As you say there is an issue with reflection. But this might be something you can work around.
Since you're interested in only a small area, you can push that far off to one side of the field of view.
This way the camera, and flash, is off center and not directly in line to cause a visible reflection.
You can then use some white paper or foam-core as a reflector to bounce some of that light from the flash back to the rig.
With the camera being off center, any reflections from your flash will be at such an angle that they will remain out of sight.
I do this all the time for photographing paintings/photos behind glass when I do not have the luxury of getting them into a proper studio-lighting type environment.
It is also how you would photograph a mirror straight on without your own reflection. :-)
Hopefully the flash will be fast enough to stop the action.
At least it is simple enough to be worth a try.