The gel / liner for Winter the dolphin - as well as Winter herself - is in fact REAL. It was not done with special effects and is actually Winter herself swimming around both without the prosthetic tail and with the prosthesis. Initially the aquarium had issues with keeping a prosthetic tail on her that was secure and comfortable. Because of this they reached out to a local medical manufacturer, ALPS South out of St. Petersburg, Florida partnered with Hanger Orthopedic Group and ALPS South developed the liner, specifically designed to comfortably and securely fit Winter's prosthetic tail.
The dolphin pendent Clay carves for Sawyer, doesn't have a tail, just like Winter.
In the evening of November 11, 2021 Winter, the 'star' dolphin of the film, passed away.
This marks the third out of five movies that Ashley Judd and Morgan Freeman have worked on together. The others are Il collezionista (1997), High crimes - Crimini di stato (2002), Olympus Has Fallen (2013), and Dolphin Tale 2 (2014).