Vistula Lagoon Vistula Lagoon The Vistula Lagoon (; or "Kaliningradskiy Zaliv"; ; ) is a brackish water lagoon on the Baltic Sea roughly 56 miles (90 km) long, 6 to 15 miles (10 to 19 km) wide, and up to 17 feet (5 m) 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
Curonian Lagoon eventually assimilated by the Germans, except along the Curonian Spit where some still live. The Kuršininkai were considered Latvians until after World War I, when Latvia gained independence from the Russian Empire, a consideration based on linguistic arguments. This was the rationale for Latvian claims over the Curonian Spit, Memel, and other territories of East Prussia which would be later dropped. The Lagoon, formed about 7,000 years BCE, is a freshwater lagoon. Water depths average 3.8 meters. It is highly biodiverse, although troubled by water pollution. The presence of algal blooms was confirmed in the 2000s. Curonian Lagoon The Curonian