Ruby (Lana Condor) and her family live in a coastal village called Oceanside. Her mother, Agatha (Toni Collette), is a successful realtor, her father, Arthur (Colman Domingo), runs a gift shop, and she has an energetic little brother Sam (Blue Chapman). Ruby does not look like the other kids at school. She’s blue. And where a human’s hair should be, she has something fishy. Agatha tells her to explain that the family is from Canada, which seems to satisfy everyone. Her mother also cautions that she can never go in the water or even on a boat. That puts a lot of limits on her social life in a beach-centric town.
Ruby has a crush on Connor (Jaboukie Young-White), a boy she’s tutoring in math, but she cannot find the nerve to invite him to the prom. When he falls into the ocean, though, she impulsively jumps in to rescue him. And then, well, you saw the title. Her transformation leads to connections to relatives on her mother’s side of the family she never knew existed, including Uncle Brill (the always-delightful Sam Richardson) and a deliciously imperious grandmother Kraken queen (voiced by Jane Fonda) known as Grandmamah (emphasis on the third syllable, please).
At first, Ruby is shocked and embarrassed by her Kraken-hood. But thanks to Grandmamah’s encouragement, and a new bestie classmate, Ruby sees how her new abilities have the potential for doing good. The new friend is the instantly popular new girl at school, Chelsea Van Der Zee (Annie Murphy of “Schitt’s Creek”). They have something in common. They are both sea creatures; Chelsea is a mermaid. Grandmamah has told Ruby about the war between the Kraken and the mermaids, but Ruby thinks her friendship with Chelsea could lead to a new era of peace and unity.