He-Man and the Masters of the Universe (2002)
The Deep End
S1 E6:
An unexpected power surge across Eternia prompts the heroes and the villains to search the Sea of Rakash for answers. It becomes apparent that the Coridite crystal, long thought destroyed, still exists in the possession of Mer-Man. Man-At-Arms manages to grab the Coridite but Mer-Man prevents the hero from escaping. Just as Mer-Man is about to retrieve the crystal, his large fish ally swallows Man-At-Arms and the Coridite crystal! Unexpectedly, the Coridite causes a mutaion inside the giant fish, making the creature extremely powerful and dangerous...