In January 1967, while the vessel SS Ixion was traversing the Arabian Sea, the ship’s crew observed a phenomenon so strange that seemed like something right out of science fiction: as far as the eye could see, the surrounding ocean was producing an eerie, milky glow.
“The sea from horizon to horizon in all directions took on a phosphorescence glow, not brilliant, but a definite glow similar to the glow of a luminous watch,” wrote the ship’s Second Officer, J. Brunskill, in an entry detailing the encounter. “The moon had just set and the whole sea was several shades lighter than the sky.”
According to Brunskill’s account, the eerie phenomenon remained visible for some time before the intensity of the odd glow began to dim, and the ocean soon returned to its ordinary nighttime appearance.
Brunskill described feeling strange sensations while the glowing sea was present.
“When looking into the sea at the height of the phenomenon, it was almost impossible to focus the eye and a slight feeling of vertigo was experienced,” Brunskill wrote. “This eeriness could well have convinced the superstitious mariners of long ago that the ship would fall off the edge of the world during the night if navigated far from the shore.”
A similar incident occurred near the same area of the Arabian Sea just nine years later, which Captain P. W. Price of the MV Westmorland, along with the ship’s Third Officer, N. D. Graham, during which they said the entire sea and even the sky near the horizon “glared a brilliant and bright green” that was so bright “that neither white caps nor swell waves could be distinguished from what appeared to be a perfectly flat sea.”
Similar encounters with odd, glowing or “milky” seas have been reported by sailors for centuries. Despite their ongoing occurrence, many questions remain about the conditions that give rise to these unusual natural displays, as well as conditions that might help predict when they are likely to occur.
Now, researchers have compiled the first comprehensive database of eyewitness accounts of “milky seas” and related appearances of marine bioluminescence in over three decades, pairing these historic reports with satellite observations from modern low-light imaging systems.
The research, published by J. Hudson, S. D. Miller in a paper featured in AGU: Earth and Space Science, explores the potential links between these glowing seas and large-scale climate patterns like El Niño and the Indian Ocean Dipole, offering new insights into the conditions that might predict when and where milky seas form.
“Milky seas are a rare, historically fabled form of marine bioluminescence,” Hudson and Miller write. Generally known to produce a constant, non-flashing, whitish glow, appearances of milky seas can illuminate large swaths of ocean—as much as 100,000 square kilometers—in occurrences that can sometimes last for months at a time.
“Eyewitnesses have compared the experience of sailing through a milky sea to a snowy plain at night, the ‘Twilight Zone,’ and even the biblical apocalypse,” the study’s authors write. They note that despite observations of the phenomenon being made for centuries, “little is known about the physical and biogeochemical processes which govern their formation, longevity, and size.”
One problem that past studies involving milky seas has encountered repeatedly is the lack of quality scientific data on the phenomenon. Additionally, the remote areas where reports of the phenomenon tend to originate, as well as the unpredictability of their occurrence, makes planning for studies of the phenomenon difficult.
To address these issues, Hudson and Miller began collecting eyewitness reports of the unusual marine phenomenon spanning several centuries, which they combined with modern satellite low-light imaging technologies.
In their paper, the authors “present the first extant database of milky sea eyewitness accounts in over 30 years, along with “the first statistical comparison between milky seas and coupled atmosphere-ocean phenomena such as the El Niño Southern Oscillation and the Indian Ocean Dipole to elucidate connections between milky seas and potential sources of predictability within the coupled earth system.”
Citing examples of early crowdsourcing that helped produce first-hand reports of milky seas in the past such as the Marine Observer, Hudson and Miller argue that the revival of such a publication in the era of social media “could serve as a valuable interface between the scientific and maritime communities around the world.
“Integrating such an initiative with the power of modern online interconnectivity (e.g., social media) could allow for experts and scientists to create curated databases of many understudied and under-observed phenomena around the globe,” they argue.
The new paper, “From Sailors to Satellites: A Curated Database of Bioluminescent Milky Seas Spanning 1600-Present,” appeared in AGU: Earth and Space Science on April 9, 2025.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.