Sean Lenz and Kristoffer Abildgaard dropped high-powered Cyalume glow sticks into Northern California waterfalls and used long exposures to capture the submerged trails in this project entitled Neon Waterfalls. Some of the more complicated shots were created by stringing several of the glow sticks together.

If your are concerned about pollution, the buoyant sticks were never opened and were collected at the end of each exposure, thus no toxic gunk leaked into the water.

(via)