With the world’s oceans in crisis, citizen knowledge and awareness around riverine and marine waste has become an increasingly crucial topic of study. For most investigations, spatial analysis has centered on the coastline, or most specifically the beach, i.e., the space where most respondents (urban, Northern, middle class), encounter marine litter. Yet, by focusing on the beach as the primary space of analysis, most studies have severely limited the scope of citizens they can engage, because in many African cities it is a space of exclusion. Moreover, for individuals further upstream, in spaces distant from the coast, what are their understandings of riverine and marine litter? What is their knowledge of the hydrological systems standing between them and the sea, and how do they see their ability to influence them? Drawing on extensive qualitative fieldwork in low-income, riverine adjacent communities in Durban, South Africa, and Blantyre, Malawi, the purpose of this article is to understand how Africa’s urban poor experience and understand riverine and marine litter. The study utilises Foucault’s notion of problematisations, and more recent adaptations of Foucault’s work toward waste as a lens to conceptualise processes of problem formation: how individual respondents view riverine and marine litter as a problem. Findings suggest that problematisations around waste, in the community and in the hydrological system, are formed through daily experience and personal hardship; in the case of Blantyre, through the perceived impact waste can have on hydroelectricity generation, and in Johanna Road, by its contribution to flooding within the community. However, understandings of the marine environment and respondents’ impact on the hydrological system, remain limited. Recommendations include rooting education and messaging around riverine and marine litter within low-income individuals’ lived realities. However, any interventions targeted towards the poor must be accompanied by broader systemic change: improving access to solid waste management services and creating cleaner and more equitable communities.