[general_re]

The Flower Garden Banks off the coast of Texas are relevant to this discussion for another reason, though:

More recent emphasis has shifted to determining the ultimate sources of larval input for the Flower Gardens. Since nearly all reef organisms have some form of larval planktonic stage, they have the potential for dispersal over vast distances (thousands of kilometers). More importantly, the Flower Gardens are isolated from other similar reef systems by more than 600 km of open water, with their nearest neighbors located north of Veracruz, Mexico to the southwest and the Yucatan peninsula to the southeast.

Source

So much for the 550 km "problem". Move along, folks - nothing to see here.

[Physicist]

Sorry, that's no help. In 666's worldview, that simply makes it an even better example than Lord Howe Island. He'll tell you that since coral larvae obviously can't travel 550 km (how he knows this is unrevealed, and YOU can take it on faith, thankyouverymuch), they definitely can't travel 600 km. So if there was an ice age 10,000 years ago, either coral evolved in situ from sand crabs since then, or God placed the reefs there by His Almighty Hand.