Counterpoint: I went on vacation to the Dominican Republic a few years back, and went to one of the more remote villages where there was a river outlet. There was a guy there who wanted to take us out on his boat, but we looked in the water and about half of it was covered with an opaque drift of plastic jugs, pieces of styrofoam, etc. I think in the US we have some antisocial assholes roaming around like the one you saw, but it's not like everyone does it by default.