The "Blue Tears" of Kuala Selangor is a natural nighttime phenomenon caused by Dinoflagellates, which are algae or marine plankton that emit blue light at night. "Blue tears" are normally spotted at the shore, but visitors to Kuala Selangor can catch algae on a speedboat ride along the waters where the river meets the sea. The sighting of the "Blue Tears" here is the first in Selangor.Â