Cays, also spelled as Keys, are small, low islands which are generally sandy and located on coral reef platforms. These islands are commonly called as keys in Florida as well as in parts of the Caribbean. A coral cay/key is a small island which is formed when coral fragments keep piling on top of a coral reef with the help of tides, winds and bird feces. In due course of time these coral fragments mount higher until this pile becomes large enough for birds to nest on and for seeds to germinate. It continues to grow in size as the bird droppings and leaf material accumulates and more coral debris collects and slowly an island is created. Sand cays/keys are typically built on the edge of a coral platform, in the direction opposite to which the prevailing winds blow. Arguably the most popular key is the Florida key, which is a coral reef found off the southern Florida coast. In 1986 a non-profit ecotourism organisation called the Coral Cay Conservation was established.
A small, low island composed largely of coral or sand.
Coral reefs are formed when coral keeps piling up and soon it gets so big that it is a nesting place for birds nd eventually becomes a cay or a key.