Plastic waste is one of the most notorious of all environmental issues–and also a hard problem to solve. From marine conservationists to engineers, many people have addressed the problem by tapping into technological solutions or attempting to raise public awareness, yet there are only limited examples of behavioural explanations for why people continue to litter in public places such as waterways. In this research, we examine the impact of settlement location (source, transition and floodplain zone) and perceived difficulties in getting the necessary resources. Focusing on river basins in Bali and East Java, we will also assess people’s willingness to contribute resources in a Public Good Game, as a hypothetical reflection of their shares in community’s greater good. We found that people living upstream contributed more to public good, but failed to correlate the effect of perceived difficulties in gaining resources to their contribution. © 2021 International Association for Hydro-Environment Engineering and Research.