Water pollution from crude oil spills in the mangrove ecosystem was investigated employing water samples obtained from three different locations in the Niger Delta. Focused group discussions were held and comprehensive questionnaires were administered to the residents in the three communities where the water samples were collected. The results of the study showed that oil activities have led to poor water quality in the Niger Delta, negatively impacting on the mangrove ecosystem with extensive depletion of fish stock in the region. The authors recommend the adoption of best practices in the oil activities to minimise the harmful effects of oil operations in the Niger Delta.