ENData on flooded relict coasts that have survived in the eastern Baltic, elements of their landscape, and archaeological research of GS-I to the Early Holocene, are presented in this article. On the basis of this research, the changes to the coastline of those times related to the fluctuations in the water level and the subsistence economy of people who settled near the coast are detailed. Based on the dates of relict trees and peat deposits, as well as the chronology of archaeological layers and archaeological finds, the research conducted in the Baltic Sea and on its shores has enabled the estimation not only of relative, but also eustatic sea level changes. During the research, the location of the final-stage Yoldia Sea and the initial-stage Ancylus Lake shores were specified, their landscapes were determined, and the development of the Ancylus Lake and the first to the third Littorina transgressions and regressions were specified. The latest research data obtained from the waters of the Baltic Sea provided in this publication are related to analogous research into the shores and changes in the water level conducted in the south and southwest parts of the Baltic Sea. Keywords: Baltic Sea, Sea level fluctuation, Flooded coasts, Underwater relict forests, Prehistoric coastal settlements, Mesolithic, Neolithic, Lithuania. [From the publication]