I agree this is an increasingly serious problem but I just can't see us making the entire ocean that bad without pretty much killing the entire planet.its pretty hard to clean up some forms of poisons especially if we make the water a genetic soup that can't be recovered as potable. desalination is only useful if the water hasn't turned toxic beyond recovery. yes we may be able to come up with some antigens but with the amount of medical waste and super bugs water could become our biggest problem. in England a study of some rivers points the finger at the polymer industry for the break down of X chromosome in the fish living in those rivers the companies bank on.(regardless of this studies voracity or not) its an example of how water can be made unsafe to consume and less likely to be cleaned by current means.