About Sea of Marmara:

• The Bosporus and Dardanelles straits connect the Aegean Sea and the Black Sea via the Sea of Marmara. It is the only passage through which the Black Sea ports can access the Mediterranean and beyond.
• Over three million barrels of oil, about 3% of the daily global supply, mostly produced in Russia, Azerbaijan, and Kazakhstan, pass through this waterway every day.

Source: EPIC March 2022