It seems you’re asking for the story of the 2012 film Padak (also known as Padak: Swimming to Sea or A Fish Story in some English releases).
Here’s a summary of the plot:
Padak, however, refuses to surrender. She tells Spotty and the others about the vast, free ocean. She devises a plan to escape. The older fish think she’s crazy, but Spotty is inspired. padak -2012-