For as long as she can remember, twelve-year-old Emily Windsnap has lived on a boat. And, oddly enough, for just as long, her mother has anxiously kept Emily away from the water. But when Mom finally agrees to let her take swimming lessons, Emily makes a startling discovery -- about her own identity, the mysterious father she's never met, and the thrilling possibilities and perils shimmering deep below the water's surface.

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.

Neptune, king of the ocean, sends half-mermaids Emily and Aaron to the land of the midnight sun to investigate the source of the dangerous storms brewing in the ocean.

When Emily makes a wish on a magic stone, she gets a glimpse of what the future holds--and it's a disaster! She tries to make things right, but each trip through time takes Emily to a future where things turn out badly for either the humans of Brightport or the merpeople of Shiprock. Plastic pollutes the ocean, garbage overflows the landfills, and the two towns are no longer getting along. Emily realizes she can't save her hometown and the ocean alone,...