Coral Reef Spawning in the Caribbean

This video from National Geographic is of a tropical setting in the Caribbean showing how coral reefs spawn by releasing eggs and sperm that somehow meet. The sperm somehow knows to only meet with an egg from the same species. Coral reefs are the biggest structures built by living creatures in the world. The coral reefs take millions of years to build, but careless divers, boaters and global warming can destroy huge parts of the reefs in little time. Scientist predict that more than half of the worlds reef will disappear by 2030.