An encircling coral reef or sandbar can create a shallower area of water near an island, called a lagoon.
A lagoon forms when a body of water is enclosed behind a barrier reef. It can also form together with the formation of an atoll, it being the body of water in the middle of the atoll. A lagoon is a body of comparatively shallow salt or brackish water separated from the deeper sea.
An atoll is an island made of coral that circles a lagoon fully or partially. They are found in the eastern hemisphere.
Thr Red Sea
Darwin's theory starts with a volcanic island which becomes extinct. As the island and ocean floor subside, coral growth builds a fringing reef, often including a shallow lagoon between the land and the main reef. Ultimately the island sinks below the sea, and the barrier reef becomes an atoll enclosing an open lagoon. A fringing reef can take ten thousand years to form, and an atoll can take up to 30 million years I hope this helped ! Source : Wikipedia
atoll
A Barrier Reef. The barrier reefs grow parallel to the shore of an island and are separated from it by a deep lagoon.
barrier reef
Barrier reefs form parallel to the shoreline but are separated by a lagoon.
Barrier reefs form parallel to the shoreline but are separated by a lagoon.
Each island is surrounded by a reef enclosing a shallow lagoon.
A body of water separated from the ocean by a barrier island, reef system, or atoll. In the most generic sense, a lagoon is a small body of water separated from a large body of water by some physical boundary.
staten island
atoll
An island with a central lagoon is called an atoll. Kwajalein in the Indian Ocean is a very good example.
A shallow body of water that is separated from the open sea is called a lagoon. Lagoons are also commonly referred to as back reefs.
Poveglia Island is located in the lagoon of Venice, Italy.
Lagoon