A coral reef can be found in tropical and sub tropical waters. They cant be found any more north or south of 30 degrees above the equator. The most famous and largest coral reef is the great barrier reef which is about 2900 other reefs all in one place. They are found on the coasts of Australia. Global warming is getting rid of lots of coral reefs though. In 50 years 50% of them will disappear (if we don't do something) so be more enviromentally friendly now!