Coastal areas are residential regions where the lives of the community depend on the sea as the main source of livelihood. Coastal areas also have high ecosystem potential and tourist attractions, especially in archipelagic regions. These conditions encourage rapid settlement development, but it is often not accompanied by the provision of adequate basic facilities, especially environmental sanitation. This imbalance causes various problems, such as low environmental cleanliness quality and increased risk of health disturbances in the community. The coastal area of Batu Merah in Batam City is one of the regions experiencing sanitation problems. The sanitation issues that occur are not entirely caused by community behaviour but are influenced by the incompatibility of septic tank implementation with the physical conditions of the coastal area. Therefore, this study aims to evaluate the existing environmental sanitation conditions, analysing the factors behind the low use of septic tanks, and examining the mismatch of sanitation technology with the physical characteristics of the coast. The research method used qualitative through observation of the environment and society. The research results indicate that coastal physical conditions, the influence of tides, and limited infrastructure are the main factors causing sanitation problems in the Batu Merah coastal area, Batam. Therefore, an adaptive solution for sanitation system based on local conditions is needed to improve environmental quality and public health.