If you’ve never heard of shark flipping, more scientifically known as tonic immobility, boy do we have a treat for you. While it may sound like a marine version of cow tipping, shark flipping is actually the (very scientific) process of rotating a shark onto its back, resulting in an almost hypnotic state that renders the shark completely still for almost 15 minutes and can be done on a variety of sharks. This state of immobility is an incredible tool for scientific research, and skilled scuba divers have been recorded doing this to sharks as large as a tiger shark.  

The resulting action is a power that looks almost otherworldly, with sharks as long as two people paralyzed by just a touch. So, how do researchers flip a shark, and why is it even a thing? 

Tonic immobility 

Tonic immobility is a reflex state of paralysis that exists in a variety of species, from mammals and insects, to many different species of fish. There are various triggers for tonic immobility – humans can enter this state in response to trauma, while chickens can be "hypnotized" by holding their head down and drawing a line from the beak outwards. A famous example of tonic immobility is trout tickling, a fishing style in which a person can stroke the belly of a trout, completely paralyzing them and allowing easy removal from the water. 

Sharks have a rather strong tonic immobility reflex. The state can be triggered by two actions – flipping the entire shark upside-down, or (in some sharks) massaging the front of the snout. Combined, a skilled scuba diver can grab the snout of a shark, massage it into submission before flipping it over, allowing them to tag them, examine their body, or simply claim the insane fact that you just flipped over a 4-meter (14-foot) tiger shark. Watch a scuba diver flip a curious tiger shark in the video below, taking note of how they manipulate the snout to render it immobile before flipping it upright. 

 How does it work? 

To do so, a diver stimulates certain pores on the front of a sharks’ nose, which have the awesome name of Ampullae of Lorenzini. These are special receptive organs that sense electrical stimuli in the water, as well as temperature changes, and it is through these extremely sensitive pores that sharks are such fearsome hunters. When hands are placed lightly either side of the snout, near the eyes of a shark, it is thought that the Ampullae of Lorenzini become overstimulated, and the shark becomes paralyzed. This is particularly effective on tiger sharks, but has a poor success rate on Great White Sharks, for unknown reasons (some speculate the nose of a Great White is too large to successfully overstimulate the pores). 

Alternatively, if a shark is forcefully flipped over, most will immediately become paralyzed, only regaining control after an average of 15 minutes. Once again, Great Whites seem to be least affected by this phenomenon, but even they are dramatically changed once flipped over, as seen by a video that went viral in 2019. 

While upside-down, the shark’s breathing slows, muscles become lax, and the dorsal fin straightens, rendering it almost helpless. The exact mechanism as to how tonic immobility occurs is still a mystery, nor do scientists know why this reflex even exists at all. Currently, the most popular theory is that the reflex acts as a "playing dead" mechanism, deterring potential predation. Female sharks also appear to show a stronger immobility response, perhaps in an attempt to deter unwanted male attention. However, its existence even in large apex predators calls to question why such a clear weakness would exist in sharks with no known predators. Other theories suggest that it is involved in mating rituals, with reports suggesting fertilization is aided by the immobile state.

 A blessing and a curse 

Scientists have been utilizing shark flipping for geographical tagging for years, despite a lack of recognition by official boards as an ethical technique. It causes no harm to the shark, and they often simply right themselves and swim peacefully away once the researcher has completed their task. Cristina Zenato, scuba diver for UNEXCO in the Bahamas, perfected this technique and used it to remove hooks from wounded sharks in the field, boasting the ability to relax sharks up to 3 meters (10 feet) long. 

Interestingly, Orcas are also very aware of the weaknesses of even the largest sharks. Orcas have been spotted using tonic immobility as a hunting tool against stingrays, and rarely, large Great White sharks, in which they flip the animal and hold it there until it becomes paralyzed, suffocating it once still.