I went for a walk along to the end of the main Koh Tao beach. The end past the boat piers, the part that isn't full of dive shops and restaurants.
It's absolutely covered with washed-up rubbish. Rubber bands, polystyrene food trays, drink bottles, plastic twine, more cigarette butts than you've seen in your life. I had a chat to a lady who was operating a windsurf/catamaran hire operation down that end of the beach, and she said the reason the main "tourist" beaches are clean is because the operators clean them daily. It's kind of sad to see.
On the other hand, she says much of the rubbish comes from the mainland. When the mainland floods in the rains it pours down the rivers into the ocean and the prevailing currents/wind wash some of it up here.
I did my little bit, and it's good that operators do clean things up to reduce the load staying in the ocean, but it's clearly a tiny part of what's going out there every day. Nasty. Most of it appears to end up here.
- Ocean trash