An island with a central lagoon is called an atoll. Kwajalein in the Indian ocean is a very good example.
staten island
blue lagoon
Each island is surrounded by a reef enclosing a shallow lagoon.
The name of the lagoon in Venice is called the Venetian Lagoon. In Italian, the Venetian Lagoon in called Laguna Veneta.
An atoll is a type of island made from a coral reef that encircles a lagoon. It is often the top of an underwater volcano.
atoll
A Barrier Reef. The barrier reefs grow parallel to the shore of an island and are separated from it by a deep lagoon.
Poveglia Island is located in the lagoon of Venice, Italy.
barrier reef
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An encircling coral reef or sandbar can create a shallower area of water near an island, called a lagoon.
"The Blue Lagoon" (1980) "Lord of the Flies" (1990), (1963)