Its flapping appendages (parapodia) suggest an angel's wings.

seaangel (pluralsea angels)

EnglishWikipedia has an article on:

sea angel

Wikipedia

1. Any of a group of small swimmingsea slugs of the suborderGymnosomata

• clionid

• analgese

• English lemmas
• English nouns
• English countable nouns
• English multiword terms
• en:Gastropods

• Pages with entries
• Pages with 1 entry
• Entries using missing taxonomic name (suborder)
• Entries with translation boxes
• Terms with Dutch translations
• Terms with German translations
• Terms with Polish translations