With his hand close to razor sharp teeth, shark expert Neil Harvey attempts tonic immobility in a large reef shark.
Tonic can be induced by turning a shark upside down, but that's not the only way. By rubbing its nose, Neil overstimulates the electrical sensors known as the Ampulae of Lorenzini. Then, he's able to 'tip' the shark until its balancing on its nose.
This unusual technique does not hurt the shark, and seems to put it in a state of ecstasy. "The shark is completely asleep," fellow diver and shark conservationist Eli Martinez notes.
If a shark enemy could master tonic, these reef sharks would be vulnerable to attack. However, it might only work on smaller sharks. Scientists believe larger sharks are much harder to induce.
Discovery Channel notes that these are highly-trained professionals, and handling of sharks (and certainly turning them into 'zombies') is not advised.
Take a peek at these sharks ... if you dare: