When Winter began to swim side-to-side like a fish during a feeding session, after losing her tail.
The relay race in the bay at the end of the movie oozes with Awesome.
On a Meta level, from the perspective of a Clearwater resident: the real-life aquarium/rescue-and-rehab center that took Winter in really was in the process of being closed down when Winter's story went viral. The proceeds from the movie saved it almost single-handedly, though there wasn't actually a massive fundraising fair and, obviously, no relay race in the bay.
It's a bit funny, actually, visiting the Clearwater Aquarium now—it's almost unrecognizeable under all the movie merchandise. At times it seems a bit much, but you can tell that they're so incredibly grateful that they can stay open, and so proud of Winter it's palpable... and they still do rescue-and-rehab work, as well as research! The state is even considering funding a sequel, so the money could go towards building a second, larger facility.