In addition to Winter, most of the cast from the first film also reprise their roles including Harry Connick Jr., Ashley Judd, Nathan Gamble, Cozi Zuehlsdorff, Kris Kristofferson, Morgan Freeman, Austin Stowell, Tom Nowicki, Austin Highsmith, Betsy Landin and Juliana Harkavy while Hope made her film debut.
Three years after saving Winter, the staff at Clearwater Marine Aquarium rescue a severely sunburned beached dolphin, named Mandy after a little girl who finds her.
Acting on Rufus the pelican’s erratic behavior one morning, Sawyer and Hazel find and rescue a sea turtle from some fishing line.
Rufus becomes obsessed with the sea turtle, named Mavis, to the point he even watches her during a CT scan at the hospital where Lorraine works.
However, Winter's behavior has become unpredictable, even dangerous; when Sawyer tries to get her out of the tank to prepare to make her a new prosthetic tail, she becomes aggressive and knocks him into the water, injuring him.
Clay, Sawyer, and Hazel test Mandy's readiness by giving her three live fish, which she catches effortlessly, so they reluctantly decide they must release her.
Clay finds them doing so and scolds them, but then states that it does not matter, because George issued an order that Winter be transferred to a marine park in Texas.
During the party, Clay is informed that another female dolphin has been rescued and is headed to CMA; one so young that she has not yet learned how to hunt and cannot return to the wild.
When they attempt to introduce the two, Hope panics and circles the pool at high speed, forcing staff members to quickly separate the two dolphins.
Sawyer thinks that a new prosthetic tail might have better results; though Phoebe, Rebecca, and Kat are initially wary of the potential repercussions, everyone agrees.
At a press conference speaking about the possibilities for a new Clearwater Marine Aquarium, David Yates, the CEO, revealed that discussions have begun towards the development of a third Dolphin Tale movie and a television series.