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
Rodeo Lagoon throughout the summer algae bloom. The lagoon is located within the geologically complex Marin Headlands and fills a valley drowned by recent sea level rise following the last glacial period. The bed of the lagoon is covered by viscous black mud that is high in organic content, except at the east and west ends, where non-organic sediment can be found. Rodeo Lagoon was mostly unaltered until the area was developed by the U.S. military into Fort Cronkhite and Fort Barry In 1937, the Army constructed a road crossing at the east of the lagoon, which resulted in a reduction in