When she incurs Neptune's wrath by finding a diamond ring buried under rocks in the ocean, Emily is put under a curse that will force her to choose to be either a mermaid or a human and split up her parents forever.

When Neptune tells Emily and her merman father and human mother to return to Brightport to try to make merpeople and humans work more closely together, Emily faces problems with old enemies, her new, half-merfolk friend Aaron, and a mystery related to a group of legendary lost sirens.

After finally convincing her mother that she should take swimming lessons, twelve-year-old Emily discovers a terrible and wonderful secret about herself that opens up a whole new world.

"A field trip to a mysterious island quickly turns into an adventure when Emily Windsnap and Aaron discover a secret lookout point from which they spot a ghostly ship that no one else seems to be able to see. The ship appears and disappears only at certain times of day, growing fainter each time. Searching for answers only leads to more questions until Emily and her friends confront the island's keeper, uncovering the incredible story of a ship caught...

"Traveling home by cruise ship should be a relaxing break after Emily's latest adventure, but things take a turn when the ship is overtaken by a pirate king and his crew. After the pirates collect everyone's riches, they steal something even more valuable: Aaron. The pirate king's eldest son takes Aaron captive, forcing him to help guide the pirates to the mythical Trident's Treasure. So Emily dives into action and joins the younger son's crew in...

Emily Windsnap doesn't know how to swim. Her mother has always cautioned her to stay out of the water. But it's hard to make friends at the beach when everyone else is having fun in the waves. So when swimming lessons start at school, Emily is excited to finally have the chance to learn. Standing beside the pool, she feels the water calling her, but when she jumps in, she gets a strange, kind of scary sensation--like her legs are stuck together. Eager...