Bioluminescent Ostracods (also know as Firefleas/Sea firefly) Found at front beach of Redang Reef Resort, The guide call as blue sand. Ostracods are microscopic crustaceans, typically 0.2mm to 2mm long but are readily fossilised and can occur in enormous numbers in some sediments. Ostracods inhabit in aquatic environment use bioluminescence during mating where the males will attract females to them. Males ostracods flash in a sequence as they swim to attract females. Bioluminescence is blue colour because all colors of light do not transmit equally through ocean water, so if the purpose of bioluminescence is to provide a signal that is detected by other organisms, then it is important that the light be transmitted through seawater. Blue light transmits best through seawater.