Based on computer-aided models and geoarchaeological excavations, palaeohabitat renderings can account for ancient site locations and contexts much different from today in terms of sea level, coastal dynamics, slope erosion, nearshore ecosystems, native forests, and other factors. A case study illustrates this research in Guam of the Mariana Islands of the western Pacific, with specific reference to the 1500-1000 B.C. time interval. This time interval includes the oldest known archaeological sites in the Mariana Islands, directly relevant for understanding the context of ancient Austronesian population dispersals in the larger western Pacific region. The results also help toward larger understanding of coastal adaptations in dynamic settings.