The Black Sea has turned a striking shade of turquoise.
A natural phenomenon called a "phytoplankton bloom'' has turned the normally dark waters of the Bosporus and the Golden Horn near Istanbul into an opaque tone of light blue.
It's caused by microscopic organisms that have inundated the Black Sea just north of Turkey's largest city.
It's so bright, it can be seen from space.
The aquatic artwork appears every summer, but this year's bloom is one of the brightest since 2012, The New York Times reported citing Norman Kuring, a NASA scientist.
Berat Haznedaroglu, an environmental engineer, says it's a normal annual event.
"This year we got a lot of rain events that carried nutrients from the Saharan desert to the Black Sea, which created an optimal environment for this phytoplankton to bloom,'' said Haznedaroglu, who works at the Institute of Environmental Sciences at Istanbul's public Bogazici University.
In a statement published with a satellite image of the Black Sea, NASA said the milky coloration is "likely due to the growth of a particular phytoplankton called a coccolithophore.''