3. Berezan IslandOchakiv Berezan is an island in the Black Sea at the entrance of the Dnieper-Bug Estuary, Ochakiv Raion, Mykolaiv Oblast, Ukraine. It is often being confused with the artificial island of Pervomaisky that is located within Dnieper-Bug Estuary. The Berezan island measures approximately 900 metres in length by 320 metres in width. It is separated from the mainland by about a mile and a half of shallow water. From Wikipedia, the free encyclopedia.