The plot of The Little Mermaid II: Return to the Sea focuses on Ariel's daughter Melody who longs to be a part of the ocean world and is ultimately manipulated by Ursula's vengeful sister, Morgana, into stealing the Trident for her.
The Little Mermaid: Ariel's Beginning is set before the events of the original film, in which King Triton has banned music from Atlantica, and Ariel, her sisters, Sebastian and Flounder rebel against this new law while a greedy palace official, Marina Del Rey, seeks to claim Sebastian's position for herself.