This is cool — tiny dinoflagellates produce a ripple of sparkling light when something brushes past.
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are also found in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. About half of all dinoflagellates are photosynthetic, and these make up the largest group of marine eukaryotic algae aside from the diatoms. Being primary producers makes them an important part of the aquatic food chain. Some species, called zooxanthellae, are endosymbionts of marine animals and protozoa, and play an important part in the biology of coral reefs. Other dinoflagellates are colorless predators on other protozoa, and a few forms are parasitic.