80% of plastic pollution in our oceans is transported from land to sea via rivers…a lot of it comes from “coastal recreational activities.” I had to look this up because I was curious. People need to clean up their trash while at the beach (river and ocean). I have never thrown garbage anywhere except for a trash can. But now that I think of it, sometimes they don't cover the trash cans up well enough to protect it from the wind on the beach and river…so trash just flies out.

https://www.sciencedirect.com/science/article/pii/S0048969716310154

https://www.nature.com/articles/s41598-018-22939-w