Red tide is the name given to blooms or population explosions of certain tiny planktonic organisms, usually in coastal waters. The organisms become so dense that the water becomes discolored, taking on a brown, red, yellow or green hue. Large areas of the sea, perhaps hundreds or thousands of square kilometers, can be affected by the phenomenon. The Red Sea takes its name from a harmless red tide that frequently appears there. The organism which is responsible is known as sea sawdust (Trichodesmium or Oscillatoria ), red tides of which are widespread throughout oceanic waters of the Indo-Pacific Region also.