Discarded plastic is a real problem. Here is a project where there are so many flip-flops washing up on an Indian Ocean beach people can specialise in re-cycling them!!! Not only does that give a feel for the scale of the waste problem but the level of poverty in many areas;
http://www.swahili-imports.com/home/si3/page_5146/uniqueco__the_flip_flop_project.html
I don't know about you but every beach/coast I go to is plagued by this problem.
How does so much waste end up in the sea?