PHOTOS: Gorgeous glowing waves wash up in California
Wednesday, May 16, 2018, 13:50 - Crowds are flocking to the coastline near San Diego, California, where neon blue waves have been crashing along the shore since Monday.
The bioluminescent waves cover a 28 kilometre stretch of water. Scientists aren't sure how long they will remain.
The rare phenomenon comes courtesy of an algae in the water called dinoflagellates. The glow is a natural defense the algae employs to deter predators.
Scientists call the event a "red tide" because the microorganisms appear red during the day. They glow at night because they're disturbed by the waves.
While only a handful land-dwelling plants and animals can make their own light, researchers estimate that between 80 and 90 percent of deep-ocean animals are bioluminous.
Most animals emit a green or blue light because these colours travel well in a dark environment.
There are a few reasons why some plants and animals may have developed this ability. It's believed to help animals attract prey and communicate with one another.
In some instances, it can also act as a decoy. Some squid and shrimp species can release a glowing cloud of ink which is used to distract predators as the animal makes a getaway.
HOW DOES BIOLUMINESCENCE WORK IN ANIMALS?
In humans, chemical energy is released as heat -- but bioluminous animals can also release heat in the form of light, courtesy of a compound called luciferin.
When luciferin is exposed to oxygen it creates a chemical reaction that emits light.