In light of your recent study of geologic time, possibly some 5+ billion years, consider that reefs have existed in our oceans for likely a billion years. As an example take New Mexico's Carlsbad Cavern area, the Permian Age (280,000,000 years ago) fossilized reefs that are now thousands of feet above sea level. The marine environment changes along our coast lines over geologic time due to Plate Tectonic collisions and mountain building, but the reefs still exist. The question is, how do they move from shore to shore or continent to continent? Aliens maybe?