To ruin Cena's career, you'd only have to drain the coastal areas and inland waterways.
Also, seeing as the supporters of SOPA are overwhelmingly old media types that've done nothing but suffer at the hands of the internet, draining the ocean may well be the point.
No, you have to drain the entire ocean. Think about it. If you drain the coast, the limit of where you drain out to is now the new coast and the coast guard still have jobs.
Best to simply just blow up the planet. I'd rather that than the ugliness of every species dying of thirst at the same time.