The Valor Ocean was a large body of water on the planet Bajor.
History and specifics
During the Occupation of Bajor, the Cardassians set off antimatter charges that opened a river channel into the land where the city of Bar'trila was located. This action would cause the water from the Valor Ocean to flood the valley where the ancient city was which caused the creation of the Inland Sea. (TOS novel: Captain's Peril)