Cordelia Blue is afraid of water. Cordelia is also a mermaid. Determined to face her fear, Cordelia enters the ocean for the first time since her twin brother was killed and learns she is from the oldest bloodline of mermaids. Entrusted with a magical relic, it us up to her alone to break an ancient curse and free the mermaids from the water. But the selachii - mysterious shark shapeshifters - also have their eyes on the relic. As tensions increase between the mermaids and selachii, Cordelia doesn’t know who to trust. Forced to choose between love and race, she doubts every decision and the intentions of those around her. Trusting her head will lead to a path of betrayal, but she might just get her family back. If she chooses her heart, the mermaids may stay cursed to remain in the ocean forever.