Because it is secure and lies flat.
No it is not. An atoll is largely made up of coral reef and is generally flat land (Tokelau is an atoll) Samoa has mountains and is not flat.
Colonies of coral take on many shapes and sizes. No two look the same. Some resemble plants, some resemble brains, some are spiraling while others are flat like a table top. All of these make up a coral reef. There are many different types of coral reef as well. There is atoll reef, barrier reef, fringing reef, table reef, apron reef, bank reef, patch reef and others. Each of these different types of coral reef grows in a different environment. For more information about the specific shapes associated with the reef types listed above, see the related link.
Reef knots are used for first aid because they lay flat and are easily undone.
A fringing reef
The Great Barrier Reef is a coral reef.
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no
The Great Barrier Reef is the largest reef system in the world.
The barrier reef off of the coast of Australia is the Great Barrier Reef. This reef is the largest coral reef system in the entire world.
No reef system is longer. The Great Barrier Reef, at over 2300km long, is the world's largest reef.
Reef sharks are sharks that inhabit coral reefs. There are several different species of them. They are the Blacktip reef shark, Whitetip reef shark, Grey reef shark, and Caribbean reef shark.