Fifteen-year-old Ruby Gillman learns that she is in the next legendary line of sea krakens. Despite her lofty destiny, she is desperate to fit in at Oceanside High. Ruby struggles even more to fit in when her mother forbids her from going to the beach. After disobeying her mother's rules, she discovers that she is descended from the warrior Kraken queens and will ascend to the throne as the Warrior Queen of the Seven Seas, her grandmother. The krakens are a race sworn to protect the world oceans from the vain, power-hungry mermaids by battling with eons. Ruby would need to embrace Chelsea, a mermaid-turned-human who enrolls at Oceanside High School.