Ok, I'm watching Modern Marvels over here

It's about mega-engineering failures.

They were talking about the "environmental devastation" that oil spills(Exxon Valdez) causes, and It occurred to me; IF oil spills are some kind of permanent ecological ruin- what about all those tankers sunk in WWII?

I don't remember anyone stopping the war when the tankers were spewing tons of oil off our Atlantic of Gulf coast. Maybe there was a covert group of eco-commandos, but you'd think by now the secret would be out- don't you?
So, just what DID happen to all those unsanitized beaches? Why aren't they still polluted (if a massive Super-fund/beaches hadn't happened in the 70's)?