The sustainability of natural resources is crucial for economic and sociological success in tourism. The threat of depletion of natural resources, increasingly exacerbated by negative factors such as global warming, plays a significant role in the success of the tourism industry. This research focuses on beaches preferred by tourists and domestic visitors in Sakarya (bordering the Black Sea) and Balıkesir (bordering both the Marmara and Aegean Seas) in the Marmara Region. The research area consists of Karasu beach in Sakarya and Gömeç beach in Balıkesir. The aim of the research is to determine and compare the opinions of local people and tourists visiting the beaches of Sakarya/Karasu (Black Sea) and Balıkesir/Gömeç (Aegean Sea). A semi-structured interview technique was used as the data collection tool. Data analysis was performed using the MAXQDA Qualitative Data Analysis Program. Content analysis was applied to the healthy data obtained from a total of 24 individuals, 12 from both Karasu and Gömeç. The research results did not reveal any significant findings regarding the benefits of the beach air, sand, and water, which was the primary objective of the study. Furthermore, it was determined that participants lacked sufficient interest and awareness regarding the historical fabric of the region, which was a secondary objective of the research. Participants were mostly married, middle-aged or older, generally had multiple children, and had a middle income level. This research was based on the theory of planned behavior, which suggests that participants' behavior is shaped by the influence of their immediate environment. While the research generally highlighted the inadequacy of infrastructure for both beaches, it also identified natural beauty and proximity to participants' residences as reasons for visiting both beaches. It is believed that future research focusing on beach quality could enrich the findings of this study.