This is a nudibranch — what may or may not be a Pseudobiceros gloriosus, and there are many, many kinds of flatworms that look like this one. Check out DiscoverLife.org’s gallery of flatworms. This National Geographic link also has some excellent nudibranch photos. And for a previous video study in locomotion, check out the Ribbon Eel. This Webby award-winning video collection exists to help teachers, librarians, and families spark kid wonder and curiosity. TKSST features smarter, more meaningful content than what's usually served up by YouTube's algorithms, and amplifies the creators who make that content. Curated, kid-friendly, independently-published. Support this mission by becoming a sustaining member today.