Enlarge / The boat trip went through an area of milky sea south of the lights of an island. (credit: Steven Miller, Leon Schommer, and Naomi McKinnon) On some moonless nights, enormous patches of the Northwest Indian Ocean and seas around Indonesia begin to glow. This event has been witnessed by hundreds of sailors, but only one research vessel has ever, by pure chance, come across this bioluminescent phenomenon, known as milky seas.