A couple of times a year in the waters of Mexico’s Sea of Cortez, a colossal column of tuna churns slowly in an underwater fish vortex. The tunnel of over 100,000 Jack Tuna, or bigeye trevally, is large enough to cast looming shadows across the ocean floor.

The clip above gives us a rare glimpse of what it’s like to be under this huge “tuna tornado.” At the 19-second mark, the camera is swallowed by the swirling silver mass. Each tuna averages over three feet in length.   

This fantastic phenomenon is the result of the tuna’s mating behavior. Many fish reproduce outside of their bodies. Here, the tuna secrete large volumes of eggs and sperm and contain it by slowly swimming around in a circle, thus creating the tornado. Because all their genes are swirling in one big mix, the ritual allows for genetic variability. Once fertilized, the eggs then float in the water for a couple days until the babies hatch. 

In 2012, Octavio Aburto, a scientist at Scripps Institution of Oceanography, published a photo of his friend David Castro next to the column of fish in Cabo Pulmo National Park marine reserve in the Sea of Cortez to show its impressive size. It took him almost three years to get that photo.

“I have been trying to capture this image ever since I saw the behavior of these fish and witnessed the incredible tornado that they form during courtship,” Aburto told Mission Blue. 

Aburto has taken many other photos of underwater wonders to bring attention to the beauty of marine wildlife. He continues to work to protect and preserve marine species in South America.

Every day we track down a Video Wonder: an audiovisual offering that delights, inspires, and entertains. Have you encountered a video we should feature? Email ella@atlasobscura.com.