Vistula Lagoon, Pol. Zalew Wiślany, shallow inlet of the Baltic Sea, 322 sq mi (834 sq km), c.60 mi (100 km) long and from 6 to 11 mi (9.7-18 km) wide, N Poland and W Russia, separated from the Gulf of Danzig by a narrow sand spit. The Nogat and Pregel rivers flow into the lagoon. A dredged channel cuts across the northern end of the inlet and links the Baltic Sea with the Kaliningrad ship canal. The lagoon's shoreline is generally marshy. Kaliningrad is the chief city on the lagoon.

Lagoon Nebula, bright, diffuse nebula in the southern constellation Sagittarius; cataloged as M8 or NGC 6526. It is visible to the naked eye and has an angular area larger than that of the full moon. The central parts are extremely bright, and some stars can be seen embedded in the nebulosity. Because of the nebula's large size, light from its stars cannot illuminate all of the associated interstellar gas and dust. Thus, parts of it appear blacker than the surrounding sky.

Lagoon Islands: see Tuvalu.

Courland Lagoon: see Kursky Zaliv.

Area of relatively shallow, quiet water with access to the sea but separated from it by sandbars, barrier islands, or coral reefs. Coastal lagoons have low to moderate tides and constitute about 13percnt of the world's coastline. Their water is colder than the sea in winter and warmer in summer. In warm regions, evaporation may more than balance any freshwater input and may result in hypersaline water and even the buildup of thick salt deposits. Coral-reef lagoons occur on marginal reefs such as the Great Barrier Reef, but the most spectacular examples, some more than 30 mi (50 km) across, are associated with Pacific atolls.

Learn more about lagoon with a free trial on Britannica.com.

also called Courland Lagoon Lithuanian Kurshacekiu Marios Russian Kursky Zaliv

Inlet of the Baltic Sea at the mouth of the Neman River. Its northern portion is in Lithuania and its southern portion lies in Kaliningrad province, Russia. With an area of 625 sq mi (1,619 sq km), it is connected to the Baltic by a navigable strait, on which is the Lithuanian port of Klaipeda.

Learn more about Curonian Lagoon with a free trial on Britannica.com.