Sammy and Ray are supervising their new offspring, when seagulls attack them and both Sammy and Ray and two of their grandchildren Ella and Ricky are captured on trawler. While Ella and Ricky are separated and sent to the seabed, Sammy and Ray are taken to an aquarium with Lulu, a lobster with dissociative identity disorder and Jimbo a bug-eyed blobfish. Escape plans are run and tried by the leading seahorse Big D. Ella and Ricky set out with Annabel and Margaret, the pink octopus mother and daughter in order to rescue their grandfathers, getting chased by a pair of barracudas when they get there. After much communication trouble, Ella and Ricky interpret from Sammy that in order to escape the aquarium several squids expel ink into the ventilation system, while all the aquarium inhabitants play dead. Before initiating the escape plan, Sammy and Ray get the tyrannical Big D out of the way. The reluctant aquarium manager opens the emergency doors allowing all sea creatures out to freedom.
