Have you ever noticed that there are ring-shaped islands in the Pacific? 
They are atolls! The name derives from the Maldivian word atholhu, which means "island-lagoon", in fact they are reefs of madreporic origin in the shape of an irregular ring that encloses an internal lagoon.
The Tuamoto Archipelago is famous in the Pacific, but the atolls are also present in other parts of the planet, such as in the Indian Ocean (Maldives). 
The atolls are formed from volcanic islands with explosive eruptions: the cone of the volcano is destroyed and the inner part is invaded by water. Over the course of millennia, a coral reef forms around the island that surfaces and emerges from the sea surface. 
Over the millennia, corals have formed cathedrals of kilometers in size and the abundance of protection and food has attracted numerous varieties of living organisms such as fish, molluscs, crustaceans, echinoderms, birds and insects to the islands, so much so that to say that the madreporic cliffs as well as the rainforests represent the environment where there is greater biodiversity on Earth. 
Would you like to live on a strip of land, completely surrounded by nature and the sea?