The ocean is glowing in San Diego. Like, literally glowing.
Earlier this week, excited beachgoers started sharing photos on social media of the incredible phenomenon.
The images show crashing waves that emit a bright blue, bioluminescent glow, giving nighttime beaches an eerie, mesmerizing feel.
While the ocean is home to several animals that can give off a similar glow, they're normally found thousands of feet underwater, where they need that bioluminescence to see in the dark, murky waters of the deep sea.
It's strange to see such an effect right on shore, but thanks to a special kind of algae, San Diego beachgoers get to see it without a submarine.
That's right — not all algae is green and slimy. This particular type, Lingulodinium polyedrum is a tiny organism that blooms every few years, often along coasts in southern California. During the day, they give off a reddish color that can make water along the beach appear like a milky red.
That's why this phenomenon is also known as the red tide.
At night, though, their circadian clocks kick in, and they respond to any tension — such as that of a rolling wave — by giving off a luminescence that makes the water surrounding them appear to brightly glow.
Right now, the neon glow of the Lingulodinium polyedrum is stretching for about 15 miles along the coast off of San Diego. Scientists aren't quite sure how much longer it will last.
The most recent occurrence was 2013, and during that run, the glow lasted for about a week. But the blooming season can vary — past ones have gone on as long as a month.