In The Little Mermaid, Ariel's fish friend is Flounder.
Flounder is a small yellow-and-blue tropical fish and Ariel's closest companion in the 1989 animated film. Despite his name, he is not presented as a literal flounder; his design resembles a royal angelfish. He often accompanies Ariel on explorations, including her visits to a sunken ship where she collects objects from the human world.
Flounder is timid and frequently panics when danger appears, especially during the encounter with the shark Glut. Nevertheless, he proves loyal when Ariel needs help. He supports her fascination with humans and even helps her pursue her dream of meeting Prince Eric. Jason Marin provided his speaking voice in the original film.
Viewers sometimes confuse Flounder with Sebastian because both are Ariel's regular companions. Sebastian is a crab, King Triton's court composer, and an assigned minder who tries to keep Ariel out of trouble. Scuttle is another friend, but he is a seagull who claims expertise about human objects and routinely misidentifies them.