The underwater Kingdom is the third episode of the second season in The Chronicles of Equestria and The Isle of Berk.
After looking at some old books, Yuna, Brian, and the others take an underwater adventure to find mermaids. And there they meet Ariel, her daughter, and King Triton. And Ariel's friends Flounder and Sebastian. However, Sideshow Bob and R2-Q5 capture Ariel to be rich and Yuna and the other must save her.
- Ariel, Flounder, Sebastian, Ariel's Sisters, King Triton, Sideshow Bob, and R2-Q5 guets star in this film.