I hope the clothes they are wearing, the signs, the doona and the boat are all made of natural, degradable fibre. It isn't just the drink containers that are plastic, it's everything they wear, carry it in and all their modern technology that is petroleum based.
Instead of banning plastic coffee cups and water bottles, their time would be better spent trying to find a way to safely and profitably dispose of it all. Turn it back into re-usable oil, maybe.