A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs.
Lagoons are common coastal features around many parts of the world.
There are two main types of lagoons: coastal lagoons and atoll lagoons.
Coastal lagoons form along gently sloping coasts where barrier islands or reefs can develop off-shore, and the sea-level is rising relative to the land along the shore. Due to the gentle slope of the coast, coastal lagoons are shallow.
Most of coastal lagoons formed as a result of the Late Quaternary marine transgression, which begun approximately 18,000 years ago and finished about 3,000 years ago, leaving a mean sea level close to the present.
Coastal lagoons are occurring along nearly 15 percent of the world’s shorelines.
There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries.
Atoll lagoons form as coral reefs grow upwards while the islands that the reefs surround subside, until eventually only the reefs remain above sea level. Unlike the lagoons that form shoreward of fringing reefs, atoll lagoons often contain some deep portions. It may take as long as 300,000 years for an atoll formation to occur.
Atoll lagoons range from small to those so wide that the coral reefs on the far side cannot be seen across the lagoon. Atoll widths range from about 2.5 to nearly 100 km (1.5 to nearly 62 mi), but the mean value is about 20 km (about 12 mi).
Most of the world’s atoll lagoons are in the Pacific Ocean and Indian Ocean.
The word “atoll” comes from the Dhivehi (an Indo-Aryan language spoken on the Maldive Islands) word atholhu ( meaning the palm (of the hand). Its first recorded use in English was in 1625 as atollon. Charles Darwin recognized its indigenous origin and coined, in his The Structure and Distribution of Coral Reefs, the definition of atolls as “circular groups of coral islets” that is synonymous with “lagoon-island”.
Many lagoons do not include “lagoon” in their common names. Albemarle and Pamlico sounds in North Carolina, Great South Bay between Long Island and the barrier beaches of Fire Island in New York, Isle of Wight Bay, which separates Ocean City, Maryland from the rest of Worcester County, Maryland, Banana River in Florida, Lake Illawarra in New South Wales, Montrose Basin in Scotland, and Broad Water in Wales have all been classified as lagoons, despite their names.
Aitutaki Lagoon is famous for being one of the most beautiful places to visit in the world, complemented by the culture of the magnificent Cook Islands.
Pileh Lagoon is nestled away on the island of Phi Phi Leh, Thailand. It is a hidden haven of warm turquoise waters, pure white sands and a dramatic backdrop of towering limestone cliffs.
Chuuk Lagoon in the South Pacific contains the wrecks of around 50 Japanese warships and 275 aircraft destroyed by Allied forces in the Second World War. Over the years, the wrecks’ decks and sides have been transformed into coral reef in this 64-kilometer (40-mile) wide expanse of pristine water, making it a very interesting scuba diving destination.
The Blue Lagoon – world’s most famous lagoon, is not a lagoon at all. It is a geothermal spa in southwestern Iceland. The Blue Lagoon is one of the most visited attractions in Iceland.