The oceans are in serious trouble. Ever notice that every few years "new" fish show up in grocery stores? They aren't new fish, they're species that used to be considered undesireable that are then renamed and sold as seafood, because the previous fisheries are depleted.
http://www.dailymail.co.uk/news/art...-slimehead-fish-renamed-boost-popularity.html
This is quite true, and is mostly because of overfishing due to very large, very effective, yet inefficient factory ships. But pollution, run-off, and high CO2 levels also stress marine ecosystems. Fish populations cannot bounce back as quickly if pollution, high CO2, etc. cause displacements of their preferred food. This can be direct, as when a species' preferred prey becomes scarce. But it can also be maddeningly indirect, such as when pollution in a particular area causes a particular toxic alga to bloom and kills off (or makes toxic) planktivores necessary as a first food for a species several links down from the species of interest. Thus tuna, obligate pelagic piscivores, may decline because herring are eating (or dieing from gill damage caused by) a particular golden alga which blooms due to pollution.
Regarding private enterprise, there is an industrial park next to me that was one of the most polluted places in Tennessee. They literally excavated trainloads of soil and carted them away to be incinerated. The pollution occurred when it was a government munitions manufacturing plant. The most critically polluted area in Tennessee is probably the area around Oak Ridge, which is heavily contaminated with plutonium and uranium. Again, government. Government is also quite fond of exempting itself from its own regulations - Google "snail darter".
Nonetheless, the EPA is vitally important. Most private companies do wish to be good stewards of the land, but even with the best of intentions may not use effective pollution and runoff controls. Also, any private company intentionally not caring about the environment could out-compete those who do care. The EPA, although subject to abuses like any government organization - indeed, like any human enterprise - still serves a vitally important function.