... And it's an undersea courtship ritual. 

All you really need to know is that these are fish, and that they have formed into an enormous underwater tornado.

What you might also want to know is that the fish in question -- thousands of them, swirling together in Cabo Pulmo National Park in the Sea of Cortez -- are Bigeye trevallies*, and that the undersea cyclone they have formed themselves into is likely part of a rarely observed mating ritual -- what scientist Octavio Aburto describes as "courtship behavior." This is Saturday night in Trevally Time ... and the club is open for business.

What you might want to know, as well, is that the tornado phenomenon was captured by Aburto (also a talented nature photographer) as he and his friend David Castro -- the only human depicted in the video -- were diving Cabo Pulmo. "In the afternoon, these fish congregate to form a large spawning aggregation around the reefs of the National Park," Aburto writes in a still version of the video above -- a photo he entered into National Geographic's 2012 photo contest.

The image is amazing. So amazing that some have claimed that the image is fake. The video above (official name: "Making David and Goliath"; real name: "OMG Fish Tornado") is in part a scientific document, and in part a piece of evidence that the CRAZY FISH TORNADO is real -- creepy, maybe, and intense, and gorgeous, and creepy again ... but real.

* I initially referred to the fish depicted here as tuna; they are, in fact, jack fish. This prevents, unfortunately, the amazing neologism "tunado" from taking its rightful place in the culture ... but it has been corrected in the text above.