Thanks!
For the water balloons, I just used daylight. It's the brightest light source I have available, after all.
For the water drops, I actually built a custom LED light source using six CREE COB LEDs. I don't remember the exact part number, but they were from the CXB1507 family. I'm running the whole array of 6 at a total of about 40W, so they're bright enough for most things.