Barbie stars as Lumina, a mermaid who dreams of being a princess. As long as she can remember, she's had a magical power that makes pearls dance and glow. Lumina and her best friend Kuda, a pink seahorse, embark on an adventure to a majestic mer-kingdom. There, she uses her powers to help her friends prepare for the Royal Ball. Lumina then discovers that her magical pearls are the key to unlocking her true destiny and ultimately saving the kingdom.