Amelia Bedelia and her mother share a summer vacation home at the shore with her aunt Mary and her cousin, Jason, who is younger than Amelia Bedelia. Amelia Bedelia is slightly resentful about having to chaperone her younger cousin. But his sense of adventure and nose for trouble quickly bond them. Through a shopkeeper, the moms hear about Melanie, a girl who is in between the ages of their two children and lives in the shore town year-round. She is shy and described as needing to ???come out of her shell. Amelia Bedelia is looking forward to meeting either a very small girl or seeing a very big shell to add to her growing collection. With Melanie as guide, the kids have various adventures. They build sand castles, swim and body surf, experience a shark scare, and spend the day at a water park. They clam, shrimp, and go crabbing, kayaking, and sailing. As much fun as their nautical adventures are, the lives of this trio get way more exciting when they stumble on what may be treasure, buried by a pirate who sailed these same waters.