The temperature of the Black Sea’s upper layer has a marked yearly periodicity. In winter, water temperature ranges from 31 °F (−0.5 °C) in the northwest to about 48 to 50 °F (9 to 10 °C) in the southeast.
Meaning it is cold for swimming?
In summer the surface layer is warmed to between 73 and 79 °F (23 and 26 °C). At depths of about 160 to 240 feet (50 to 75 metres), a cold layer remains at 45 °F (7 °C), and lower depths do not change from their winter levels.