I think the problem if we are in you scenario is that 200 people own parts of the oil tanker and the beach is owned by 200 people and not everyone wants to pay for the costs of cleaning up the contamination, and that we have to get permission from the owners of each separate plot of beach and mone from each of the 200 people to pay for the cleanup to make the analogy of people roughly equivalent to countries and our current predicament - one or two powerful, rich people could pay for the whole thing but if they decide they don't believe in cleaning up and letting things be they could mess up things for all 200 by themselves.