The Bulgarian coastal defence according to a CIA report dated 4 September 1953

An item reported that the Bulgarian Black Sea coast was considerable fortified. While the coastline between Varna and Monastero (Monastir Sveti Konstantin, north of Varna) was very high preventing landing were there no fortifications. Between Varna southwards to the Kamichiya River was the coastline however low and were fortifications needed to prevent landings. Along this part of the Bulgarian coastline were several reinforced concrete coastal artillery emplacements built. The military at Varna herself was also fortified. After widening was the canal between Varna and Lake Devynya approachable for small steamships.

Source
The report was published on www.archive.org, document number CIA-RDP80-00810A002200170042-3