The Vistula Lagoon is a brackish water lagoon on the Baltic Sea roughly 56 miles long, 6 to 15 miles wide, and up to 17 feet deep, separated from Gdańsk Bay by the Vistula Spit. It is now known as the Vistula Bay or Vistula Gulf. The modern German name, Frisches Haff, is derived from an earlier form, Friesisches Haff.The lagoon is a mouth of a few branches of the Vistula River, notably the Nogat, and the Pregolya River. It is connected to Gdańsk Bay by the Strait of Baltiysk.
The Poland–Russia border runs across the lagoon.
Coordinates 54°29'55.491" N 19°47'35.384" E