Glowing colorful light underwater looks like magic, but like most things, it can be explained with science.
These colors are created by tiny single-cell organisms called dinoflagellates. These unique little creatures can be found across the world, some feast on sunlight, others on fellow organisms. Not all of them are bioluminescent, and scientists believe that only some may have evolved this beautiful trait as a defense mechanism, activating at the sign of movement to try to spook potential predators away.
We are still not entirely clear on all the details, but scientists believe that the cells harness the ability to activate a series of chemical compounds which produce light energy with motion, and usually blue light, probably because it travels quickest in water.
Not all dinoflagellates are safe for us, either. Some contain a toxin called Saxitoxin which attacks our neurons and can cause numbness, paralysis and even death. They can be a great source of nutrition for marine life, but they can also be detrimental to the health of not just us, but ocean critters too. This is pretty rare though, so don’t be afraid when you see them, be grateful that they’re quite rare!