The sea level changes during the Holocene have left many wave cut-offs on the limestone cliffs. They are living evidences of sea-level fluctuations. To follow this sea level changes, the authors have carried out research in the H¹ Long Bay, where limestone cliffs are most widespread. The result of study revealed that at least 3 levels of wave cut-offs related to marine regression during the Middle-Late Holocene can be distinguished in the H¹ Long Bay area: 5,3 - 6,8 m a.d; 3,8 - 5,3 m a.d; 2,0 - 3,80 m a.d. Twelve from 23 collected samples of oysters and gastropods were analysed by C¹⁴ in Australia. The result of study proved also that in the study area, after reaching maximum at about 5000-6000 yrs BP, the sea-level had dropped sinuously. The rate of marine regression during the Middle-Late Holocene was also calculated for the H¹ Long Bay area. At the end of the Middle Holocene the rate of marine regression was significant, but during the Late Holocene this rate had decreased.