Milky seas are unusual phenomena which have been noticed by mariners for centuries, but which remain unexplained by scientists. These events are when the surface of the ocean, often from horizon to horizon, glows with a continuous uniform milky light. Although the origins of this light are not well investigated, the most plausible explanation is that it is caused by blooms of bioluminescent bacteria. Dinoflagellates, which cause red tides, flashing waves, and sparkling wakes behind boats, need to be physically stimulated to produce their brief bright flashes. This type of display does not match the kind of display seen in milky seas. Bacteria, on the other hand, will glow with a continuous light, under the right conditions.