Captain Planet and the Planeteers (1990)

Season 3: Episode 2

Gi, while repairing the Eco-Sub, became irritated with Suchi's presence, and ignored his warning to install the new part to the sub's turbines. Now, they have no control over it's direction. This causes problems when they go after Sly Sludge, who is dumping toxic waste into an Asian sea. The waste causes mutations in the sea life, especially a squid, which grows large in size, and begins to attack people, and later a nearby city. The Planeteers must stop Sludge's illegal sea dumping, and rescue the city from the mutated creature.