One of the most fascinating creatures of the sea, these small but mighty jelly-bodied, shell-less mollusks are part of the sea slug family. Nudibranchs inhabit ocean waters throughout the world, from the Southern Ocean to the Arctic and everywhere in between. Depending on the species, adult sizes can range from 0.25 to 12 inches. These soft-bodied gastropods derive their name from the Latin word Nudibranchia, meaning naked gills, which is why most have feathery gills and horns on their backs.

Nudibranchs are famous for their extravagant coloration and ornate patterns, making them a favorite sighting amongst divers. Three thousand known species of nudibranchs live in all saltwater habitats and depths from the intertidal zone to over 700m (2,300ft) deep; however, the largest variety resides on shallow, warm reefs. As benthic animals, these beautiful, oblong-shaped invertebrates are usually seen crawling along the substrate, grazing on algae, coral, anemones, sponges, and more. Check out the map below to see where you can find your favorite nudibranch species.