What is black sea nettles?

Black sea nettles (Chrysaora achlyos) are a species of jellyfish found in the eastern Pacific Ocean, particularly along the coast of California. They are one of the largest jellyfish species, with bell-shaped bodies that can reach up to three feet in diameter and long trailing tentacles that can reach up to 20 feet in length. Their coloration varies from dark purple to brownish-black, hence the name "black" sea nettles. The tentacles are lined with stinging cells called nematocysts, which they use to capture small fish and plankton for food. While their sting is not usually harmful to humans, it can cause irritation and discomfort. Black sea nettles are known for their bioluminescence, which means they are able to produce light. When disturbed, the jellyfish produce a beautiful blue-green glow that is visible underwater.