Nudibranchs are a kind of sea slug. Granted they are far more beautiful and are often very colorful, perhaps for defense. Many brightly colored species of the sea are toxic to fish when eaten. Nudis, as they are called by divers, are usually about 2 to 3 inches long with feeling tentacles in front and gills toward the back. The roots of the word nudibranch mean naked + gills. See also Dancing Nudi.
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