Physics is often perceived by students as abstract and detached from everyday experience, a recurring concern in physics education literature. Place-based learning and ethnoscience approaches, using local phenomena to connect science with students' lived experience, have been recommended to address this issue. This preliminary needs-analysis study identifies the potential of coastal well water phenomena in Majene Regency as an authentic context for fluid mechanics, while mapping misconceptions, interest, and teacher needs for contextual materials. A mixed-methods approach followed the first two stages of the Model of Educational Reconstruction (MER): content analysis and investigation of student and teacher perspectives. Data were collected from 42 Grade 11 students at SMAN 3 Majene using a Three-Tier Diagnostic Test and an interest questionnaire, and from 5 physics teachers via a needs-analysis questionnaire, with ethical approval and informed consent. Instruments were expert-validated (Aiken's V = 0.73; KR-20 = 0.78; Cronbach's alpha = 0.82). Results show coastal well water phenomena relate directly to four core concepts density, hydrostatic pressure, Archimedes' principle, and discharge-continuity and students hold significant misconceptions, particularly on Archimedes' principle (69.05%). General interest in physics was low, but interest in locally contextualized learning was high, and all teachers reported urgent need for contextual materials. This study fills a gap in place-based physics education literature in coastal West Sulawesi and yields a preliminary concept map as a foundation for contextual teaching materials, applicable locally and transferable elsewhere.