Seawater intrusion is a growing pressure in coastal communities worldwide, putting millions of people at risk of excess salinity in drinking water. This study examines the impact of saline water on people's health and labor allocation as potential pathways towards chronic poverty. Using a transdisciplinary approach based on a coupled human-water system framework, we test these linkages combining field data on well water salinity levels and rich household survey data in coastal Tanzania. The results suggest that increased salinity levels lead to more time spent collecting drinking water and an increase in illnesses. Moreover, households in poorer villages with weaker public infrastructure have limited access to alternative sources of drinking water, making them more vulnerable to scarce potable water resources stemming from high salinity. To prevent chronic poverty, communities vulnerable to saline drinking water need better adaptation strategies as well as groundwater monitoring and management.