Milky seas is a condition on the open ocean

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 where large areas of seawater

Seawater

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

 (up to 6,000 square miles) are filled with bioluminescent bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

, causing the ocean to uniformly glow an eerie blue at night. The condition has been present in mariner

Sailor

A sailor, mariner, or seaman is a person who navigates water-borne vessels or assists in their operation, maintenance, or service. The term can apply to professional mariners, military personnel, and recreational sailors as well as a plethora of other uses...

's tales for centuries – notably appearing in chapter 24 of Jules Verne

Jules Verne

Jules Gabriel Verne was a French author who pioneered the science fiction genre. He is best known for his novels Twenty Thousand Leagues Under the Sea , A Journey to the Center of the Earth , and Around the World in Eighty Days...

's Twenty Thousand Leagues Under the Sea

Twenty Thousand Leagues Under the Sea

Twenty Thousand Leagues Under the Sea is a classic science fiction novel by French writer Jules Verne published in 1870. It tells the story of Captain Nemo and his submarine Nautilus as seen from the perspective of Professor Pierre Aronnax...

– but until recently it has not been rigorously documented.
There have been 235 documented sightings of milky seas since 1915 - mostly concentrated in the north-western Indian Ocean

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 and near Indonesia.

In 1985 a research vessel in the Arabian Sea

Arabian Sea

The Arabian Sea is a region of the Indian Ocean bounded on the east by India, on the north by Pakistan and Iran, on the west by the Arabian Peninsula, on the south, approximately, by a line between Cape Guardafui in northeastern Somalia and Kanyakumari in India...

 took water samples during milky seas. Their conclusions were that the effect was caused by the bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 Vibrio harveyi

Vibrio harveyi

Vibrio harveyi is a species of Gram-negative, bioluminescent, marine bacteria in the genus Vibrio. V. harveyi are rod-shaped, motile , facultatively anaerobic, halophilic, and competent for both fermentative and respiratory metabolism. They do not grow at 4°C or above 35°C. V...

.

In 2005, Steven Miller of the Naval Research Laboratory in Monterey, California

Monterey, California

The City of Monterey in Monterey County is located on Monterey Bay along the Pacific coast in Central California. Monterey lies at an elevation of 26 feet above sea level. As of the 2010 census, the city population was 27,810. Monterey is of historical importance because it was the capital of...

, was able to match 1995 Satellite images with a first-hand account of a merchant ship. U.S. Defense Meteorological Satellite Program

Defense Meteorological Satellite Program

The Defense Meteorological Satellite Program monitors meteorological, oceanographic, and solar-terrestrial physics for the United States Department of Defense. The program is now run by the National Oceanic and Atmospheric Administration. The mission of the satellites was revealed in March 1973...

 showed the milky area to be approximately 15,400-km² (roughly the size of Connecticut

Connecticut

Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...

). The luminescent field was observed to glow over three consecutive nights.

While monochromatic photos make this effect appear white, Monterey Bay Aquarium Research Institute

Monterey Bay Aquarium Research Institute

The Monterey Bay Aquarium Research Institute is a not-for-profit oceanographic research center in Moss Landing, California affiliated with the Monterey Bay Aquarium. It was founded in 1987 by David Packard of Hewlett-Packard fame...

 scientist Steve Haddock (an author of a milky seas effect study) has commented, "the light produced by the bacteria is actually blue, not white. It is white in the graphic because of the monochromatic sensor we used, and it can appear white to the eye because the rods in our eye (used for night vision) don't discriminate color." http://www.boingboing.net/2005/10/04/first_milky_sea_phot.html