Even small thing can damage a country's economy. I think even littering can destroy the economy. There are some people in my country who throw garbage to the river and when rainy season comes, water that cannot flow smoothly eventually causes flooding and indirectly inhibits economic activity in that area.
Yeah, I see a lot of garbage collected by floating booms, from people throwing garbage all over. If that time, money and effort went to better things that would make society run smoother, such as fixing roads, then it would better the economy.