There are somethings in life one should learn NOT to play with,,, I could give you a list,, but Sharks are one of thme on that list...
Shark movie - Jaws had its run for sometime, the only other movie would be Deep Blue Sea.. had cool effects, thoughts and ideas,,, At this time, it's true, that Sharks haven't caught cancers of any kind,,,
Shark Myth,,, I think it's called "Kantra"
wher as "YOU" would get in a tank with a shark (live) allow the shark to come to you ( almost biting you in half

) where as you use the palm of both of your hands to capture the nose portion of a shark, to where you put the shark in a state of suspension,,, to where the shark will be dayzed and relaxed to apear to asleep........

or if the shark awakes,, it will tear both of your arms off,,,""" not good,,,,,

Althought the theroy is by bringing both of your palms together, with your finger tips open , the idea" is that the sharks nose gets placed between your palms,(fitted position) in moments the shark get relaxed,,,,, and yes,, it suppose to be able to be done with a Great White as well,,,,,
UUmmmmmmmmm........ maybe something more simple....
next thought,, you can't teach a shrak to swim backwards,,, try placing him in a tube with only 2 directions to go,, forward and backwards,, with out room to turn around....