Captain Planet and the Planeteers (1990)

Season 2: Episode 25

The Planeteers are shocked to see a mother whale killed during a whaling expedition engineered by Blight and Plunder. They are even more shocked to learn that it's legal, thanks to a loophole in the international laws that allow whaling for "research." They set out to prove that Blight's research for a "whale repellent" is bogus and are helped by a young Japanese teenager who is trying to dissuade his whaler father from working for the villains.