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.

Reunited with her merman father and now living on an island located in the Bermuda Triangle, twelve-year-old Emily accidentally awakens the fearsome kraken and also faces a bully from her past.

When Emily's mom finally lets her take swimming lessons, the 12-year-old 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.

Despite Emily and her boyfriend Aaron promising their best friend Shona a fun, adventure-free vacation on a relaxing tropical island, adventure finds them anyway. As semi-mers, Emily and Aaron discover an island that only they can get to, where they learn of an imminent earthquake that threatens the entire region. They must then fulfill a prophesy and find the giant who is supposed to save them.