According to what I've gathered from previous HN discussions on the same subject, oceans are self-cleaning - garbage will slowly wash ashore, so if theoretically nobody would throw garbage in the seas anymore, the oceans would be clean in some years [1].
This raises the doubt that instead of focusing on directly cleaning the waters, effort should be put into not polluting the seas in first place (cleaning shores would be consequential). But focusing on the cause rather than the symptoms is not exactly a forte of human behavior.
that would make sense given unlimited/non-competing resources, but if the resources (money, people, awareness, legislative effort) available to solve the problem are limited, it is wasteful to use them for something which doesn't work rather than something that would.
(I do not know if the specific thing works or not, just pointing out that "why not both" is not always a good approach)
This raises the doubt that instead of focusing on directly cleaning the waters, effort should be put into not polluting the seas in first place (cleaning shores would be consequential). But focusing on the cause rather than the symptoms is not exactly a forte of human behavior.
[1] http://inhabitat.com/the-fallacy-of-cleaning-the-gyres-of-pl...