'Milky Sea' Phenomenon Captured in Photo for First Time

The mysterious white ocean described by a yacht crew in 2019 has now been formally documented and confirmed with satellite imagery.

In the summer of 2019, crew members on the Ganesha superyacht were looking out to sea when they noticed the sea had turned white, almost to the point where it looked like they were sailing through snow.

"Both the color and intensity of the glow was akin to glow-in-the-dark stars/stickers, or some watches that have glowing parts on the hands ... a very soft glow that was gentle on the eyes," described one crew member, according to documentation of events published in PNAS (Proceedings of the National Academy of Sciences).

The captain of the yacht observed that the glow appeared to emanate from around 30 feet below the surface.

So-called "milky seas" are an incredibly rare phenomenon, and had only been described previously by word of mouth from marine voyagers.

"I'd say there's only a handful of people currently alive who have seen one. They're just not very common—maybe up to one or two per year globally—and they're not typically close to shore, so you have to be in the right place at the right time," Steven Miller, a professor of atmospheric science at Colorado State University and the report's author, told The Guardian.

The Ganesha crew managed to capture some very low quality pictures of the milky sea phenomenon, which were used to corroborate the story with satellite images taken of the Java Sea, south of Indonesia, during the same period, which were published by Miller in the journal Nature in 2021.

These images showed the milky seas spanning over 39,000 square miles.

Milky seas are caused by rare bioluminescent bacteria, which instead of glowing blue or green, glow white. Current theories predict that this rare glow might be due to a saprophytic relationship (feeding on decaying organic matter) between luminous bacteria and a species of microalgae expressing on a large scale, with the bioluminescent response being triggered once a certain level or quorum of population has been reached.

Strangely, according to the documentation of events published in PNAS, when the Ganesha crew took a bucket sample of the milky sea water, and stirred it, the glow got darker. With other bioluminescence, the glow usually gets brighter when disrupted.

"It takes a unique set of nutrient and wind conditions for this to lead to large bioluminescent slicks lasting days," David Gruber, professor of biology at City University of New York, told Newsweek. "These bioluminescent bacteria turn on their bioluminescence only after reaching a certain cell density, known as quorum sensing. Milky Seas or Burning Seas is the result of trillions upon trillions upon trillions of luminescent bacteria with each cell emitting a relatively faint glow. Yet, when combined, their glow can be seen from space using remote sensing and blooms over 15,000 square kilometers have been witnessed."

The mystery of what causes the white glow that seemingly behaves in the opposite manner to other bioluminescence is yet to be solved, however. Some explanations include a prediction that the species of phytoplankton may have a calcium cell wall, meaning that the glow appears paler.

"It might be [Emiliania huxleyi]," Jan Geert Hiddink, a professor at the School of Ocean Sciences at Bangor University in the U.K., told Newsweek. "It has a calcareous outside, which looks white."

Either way, this confirmation that milky seas can indeed be picked up by satellite imagery means that studying them and unraveling their mysteries will be easier in the future.