In the context of the BARREEF project’s artificial reef construction in Samsø, Denmark, this study presents a preliminary baseline assessment of biodiversity and coastal erosion, as well as future predictions. The BARREEF project aims to address the challenges of climate change and other stressors on marine ecosystems through dual objectives of coastal protection and biodiversity enhancement. The methodology includes biodiversity monitoring using unbaited remote underwater video systems (UBRUVS) at three distinct sandy sites and assessing biodiversity with indicators such as species richness or community composition. Additionally, nearby reef areas classified as structurally complex environments were surveyed to gain further insights into potential future biodiversity impacted by the reef construction. For coastal erosion analysis, shoreline analysis using the vegetation line and the high water line as indicators, satellite imagery, and historical data were utilized, while exploring diverse monitoring technologies, including drone seabed mapping, to assess coastal processes effectively. Moreover, various monitoring technologies, including drone seabed mapping, were explored to identify suitable tools for effective monitoring in this type of study. The findings reveal diverse ecosystems with multiple species thriving in the sandy environment, with structurally complex habitats exhibiting notably higher biodiversity. The planned reef’s transformation of the sandy environment into a structurally complex one adds particular significance to observed biodiversity patterns. The creation of more ecological niches by the reef is expected to foster increased species diversity and support larger organisms, aligning with higher biodiversity in such habitats. Furthermore, the creation of critical nursery habitats contributes to the long-term sustainability of marine communities. Anticipated local mitigation of coastal erosion by the artificial reef further highlights the project’s significance in coastal protection. Post-construction monitoring in 2024 and beyond is vital to gauge the actual impact of the BARREEF project on biodiversity and coastal protection. These insights into coastal ecosystems, biodiversity conservation, and coastal protection strategies have the potential to inspire similar dual-purpose initiatives globally and offer innovative solutions to urgent environmental challenges.