We have to bite the bullet, spend the money and clean up our own mess. It's not really a problem. The rigs become artificial reefs and increase fish populations, they become self contained ecosystems. Oil spills cause short-term damage and marine creature kills. But recovery is rapid and not long-lasting in its effects, as compared with homogenised pollution which goes over the seabed and throughout the water column.
Oil spills are a surface problem.
Even so, because they're the result of human error, we should increase the penalties to prevent them happening. Tankers - I don't know what you can do about them. They go from jurisdiction to jurisdiction and short of building double-hulled ships I can't see a solution. However, the tanker people are aware of the pressure of negative press. As to effects on the ocean, I believe we can do much more by eliminating human waste.