Shabla Lake Protected Area is a wetland of international importance included in the Ramsar Convention. "Shabla Lake" is the best preserved, in terms of human activity, wetland on the Bulgarian Black Sea coast.
Shabla Lake is located next to the beach, 5 km northeast of the town of Shabla. Originally is Lake Liman, formed by the bay of the old valley (dry valley) of Shablenska River. The lake has an open water area of 79 ha (together with Lake Ezerets - about 150 ha) and a maximum depth of 9.5 m.
To the east it is separated from the sea by a long sand-dune strip (about 100 m long and 30-50 m wide), and to the north by the neighboring Ezerets Lake it is separated by a narrow sandy hair, through which an artificial canal has been dug. Shabla Lake is stagnant, but freshwater - its salinity is only one per mille. In its western part the lake is fed by underwater karst springs, and in the east, through the sandy strip, there is a certain infiltration of sea water.
You can read the whole article here: https://www.nasamnatam.com/statia/Shablensko_ezero-2181.html