The story follows best friends Claire (Emma Roberts) and Hailey (JoJo), who are spending their last summer together before Hailey moves away. One night after a storm, they discover a mermaid named Aquamarine (Sara Paxton) in a swimming pool. Aquamarine, who has escaped an arranged marriage in the ocean, must prove to her father that true love exists in order to stay on land. She enlists Claire and Hailey’s help to win the heart of a local lifeguard, Raymond (Jake McDorman), within three days.
The girls, who initially hope to use Aquamarine’s wish-granting powers to keep Hailey from moving, teach her about human romance. However, their plan faces obstacles, including mean girl Cecilia (Arielle Kebbel), who also has her sights on Raymond. Along the way, Aquamarine learns that love isn’t just about romance—it also exists in friendship. When Raymond does not declare love within the time limit, Aquamarine’s father tries to take her back to the sea. However, Claire and Hailey’s loyalty proves that true love exists, convincing him to let her stay.
The film celebrates themes of friendship, self-discovery, and empowerment with a lighthearted, magical tone. With its vibrant visuals, humor, and heartfelt moments, Aquamarine became a beloved teen film, particularly among young girls in the 2000s