There are constant currents at the sea surface directed from west to east. They are weak and thus can temporarily change direction due to the wind. The tides are semidiurnal (rising twice a day) with the amplitude between 5 and 25 cm. The tidal wave weakens toward the coast due to shallow waters. The sea level is maximal in summer, due to the river runoff, and in autumn due to the winds. It is the lowest in March–April, with the total annual fluctuations within about 70 cm. Winds bring storms with waves reaching 3–5 m in the western part whereas the eastern regions are relatively calm. The storms typically last 1–2 days in summer; they are more frequent in winter and may extend up to 3–5 days.