A 'shark whisperer' in the Bahamas balances a shark on the palm of his hand, after sending it to sleep.
The diver uses what's known as tonic immobility (TI) to induce a state of temporary paralysis in a shark.
The usual method used to induce TI in shark species such as Blacktip and Whitetip reef sharks, Lemon and Leopard sharks is to invert the animal. According to The Shark Trust the unnatural posture is thought to alter the shark's sensi-motor interchange with the environment, causing it to go limp. The shark usually enters a state of TI in under a minute and may remain immobile for up to 15 minutes.
Some shark species respond in a similar way when hands are placed either side of the nose in the area surrounding their eyes.
TI doesn't cause the shark any harm and is often used by experts when handling them in the field to prevent struggling and possible injury to the animal.
TI is known to occur in other animals, particularly when they are threatened by a predator, but experts are unclear as to why the shark - itself a top predator - would develop such a reflex.
In the video below you can see a diver, known only as Tom, with a shark he has placed in TI.
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.
Don't forget that PFK is now available to download on the iPad.