Nudibranchs are shell-less mollusks belonging to the sea slug family and possess some of the most captivating patterns, shapes and colours. The "feathery gills and horns" usually seen on their backs are their gills which they use to breathe underwater. The word "nudibranch" comes from the Latin nudus "naked" and the Ancient Greek βράγχια (bránkhia) "gills".
They can be commonly found on the ocean floor, anemones and corals eating most of their time away. They graze on algae, sponges, anemones, corals, barnacles, and even other nudibranchs. To identify prey, they have two highly sensitive tentacles, called rhinophores, located on top of their heads.
Being simultaneous hermaphrodites,they can mate with any other mature member of their species. Their lifespan varies from less than a month to one year. To protect themselves, some of the species with bright or striking colours serves as a warning to predators that they are toxic. Others do the same through camouflage, emitting chemical odors or their stinging cells on their bodies.
They are very popular with photographers because of these traits of them. There are more than 2,000 known species with new ones popping up almost daily. They are difficult to spot due to most of them being tiny, so keep a look out for these adorable creatures next time when you diving.