Just keep swimming? More like just keep spinning! 

Spinning _fish _2016_05_25


A clip of these pufferfish trapped in a strange spinning cycle resurfaced online recently, and it's been wowing and mystifying Reddit users. Just in case you missed it the first time around, here's the bizarre natural phenomenon in all of its glory via the Smithsonian Channel:

The unlucky pufferfish have encountered an underwater vortex, a swirling lasso of bubbles that has formed just metres away from the wall of a reef in the Socorro Islands of the Pacific. Here, a change of seasons has brought shifting temperatures and clashing currents. It's thought the vortex emerged as warm equatorial waters collided with cold currents from the depths off the Californian coast to the north. It's also possible that local up-swells near the reef itself were the cause.

Vortices can occur even in our own homes – just picture water disappearing in a whirl down the plug-hole. But those are vertical spirals influenced by gravity. Just why the puffer-snaring vortex in the video is horizontal remains a bit of a mystery.

"Usually, ocean vortices have their axis vertically," explains Roger Grimshaw, theoretical oceanographer at University College London. "But these are quite small-scale, so that constraint may not apply." In the video, the odd turbulence could be the result of meeting currents, combined with the rough topography of the nearby reef, he suggests.

Whatever the cause, the water gets in a spin – as do the unfortunate puffers when they get too close. While the other reef inhabitants swim by, the puffers appear alone in their predicament as their fins are too small and weak to propel them to freedom. 

Of course, you might know pufferfish for the ballooning trick that gives them their name – the fish can puff up impressively when faced with a threat. But it's anyone's guess whether a well-timed defensive inflation (which is actually a pretty stressful move that takes its toll on the fish's body) could have helped propel the puffers out of this bubbly vortex.

The fate of these particular fish remains a mystery, but we hope the spin cycle eventually slowed to the point where they could make a getaway. And judging by the video below, an underwater vortex can spell trouble for divers too: 


Top header image: Chen Qu, Flickr