<p>Public perception of groundwater security is critical for addressing the challenges of rapid urbanization and climate change in coastal Asian cities. Overexploitation of groundwater, declining aquifer levels, land subsidence, and increased flooding have intensified concerns about water scarcity and security in these regions. This study examines factors influencing communities’ perceptions of water-source use and their relationship with hydrological disaster-risk perception. Data on water-consumption preferences, hydrological-disaster awareness, water-security concerns, and views on sustainable water management were collected through structured questionnaires and semi-structured interviews with 320 household heads in coastal neighbourhoods of Semarang City, Indonesia. The sample comprised 163 households residing within the public water supply company (WSC) service area, 73 primarily relying on community-based water supply projects, and 84 using deep wells as their main water source. Information on water-source conditions, quality issues, and environmental impacts was gathered through field surveys. Despite the presence of WSC infrastructure, only 21 of the 163 households in the WSC service area (12.88%) reported using WSC water as their main source, citing concerns about water quality and high tariffs. Many of the remaining households continued to rely on deep wells, even while acknowledging risks such as groundwater depletion, land subsidence, and tidal flooding. While cost, supply interruptions, and perceived public-water quality shaped these choices, low income and limited education emerged as key factors influencing how communities perceive and respond to groundwater overexploitation. Addressing groundwater security in Semarang’s coastal areas requires integrated socio-economic interventions, expansion and reliability of piped-water services, and targeted public-awareness campaigns to support more sustainable water-use practices.</p>