An area of the Black Sea has turned bright green, according to locals.
The patch, which is spreading “quickly”, is located in Omega Bay, near Sevastopol in Crimean Peninsula, became a toxic shade of green last week.
Local reports say the water was affected by a plastic bag containing unidentified liquid was thrown into the water.
Others are saying the colour change suggets a “special” having been added for “fish.”
Netizen Masha said: “I had an aquarium when I was younger, and usually water changes its colour when you add a special drug for fish.
“Based on the amount of dead birds this year, maybe somebody has decided to heal the fish.”
An investigation by a Russian health watchdog has not reached a conclusion, meaning the water may be damaging to humans.
This isn’t the first time this hue-alteration has happened.
Back in April last year, another area near the Crimean Peninsula turned yellow due to bad weather.
Environmental experts said it was a combination of sand, microelements and minerals that rose from the bottom of the sea that made the water turn yellow.