Video: Smithsonian Channel's Secrets of Shark Island is a wonderful documentary about the ecosystem in the waters around the Revillagigedo Islands, a group of four volcanic islands 386km off of Mexico. Because it's "the only natural juncture for miles" in the Pacific Ocean, there's a lot going on around there. Most scarily, a shit ton of migrating sharks. My God, just look at all them.
UPDATE: Apologies to readers, it appears the video is region-locked and can't be viewed in Australia.
The whole documentary is worth watching, if only to see the beautiful footage of all the fish in these parts of the ocean. Smithsonian Channel writes:
Enter a world where whitetip sharks, giant lobsters, and moray eels share living quarters, humpback whales breed, and mantas and tuna feast on bait in this land of plenty.