Nick Fish is an individual who is one half man, one half fish. He has webbed feet like a duck and a throat like a frog. He got this way from being cursed by his mother, who was so frustrated with him swimming in the water all the time and not heeding her. After his transformation, Nick Fish never set foot on dry land again. This upset his mother so much that she died soon after. (So, you know, don’t curse your children if you can’t deal with the consequences.)
Nick Fish later gets the attention of the king, who then sends him on a series of escapades exploring the waters of the region. Nick Fish finds many curious things, some of which concern the king and prompt him to keep sending Nick Fish back for another look. Despite his fears, Nick Fish goes but is never seen from again.
Source: Calvino, Italo, “Nick Fish”, Italian Folktales, Penguin Modern Classics, 2002. Translated by George Martin.