Good video. Lots of “coral reef” themed videos around but surprising few that give a well-rounded out explanation of what they actually are (like this one) for the less-aware.
makes me wonder if in fact humans have not built the largest infrastructure. Coral is literally cementing (limestone) and the reefs can get up to a thousand miles long. I don't know what that volume is total, but the only thing I can think of that we have built of that magnitude is the Great Wall, which must be dramatically thinner than the reefs.
