Shark riders

Several years ago we saw a program on Gator rasslin.
It turns out that an evolutionary reflex has made it so that these large lizards can't shut their mouths when their snouts and inner mouths are manipulated in a certain fashion. They are stuck in lock-jaw and you can then safely sit on them or put your head in their mouths or shove your arm down their gullet... (hey, whatever your fetish is, I'm not judging). [link]1
When I explained to her why the man could put his head in its mouth she asked me then if sharks had that same reflex.

Much spare-time research and several emails have gone into finding an answer for her but no luck yet.
Seems there are safer fields of study to choose from and no one has drawn that short straw yet.
The other day I came across a video [link]2 showing a man shoving on the nose of a surfacing shark and the reflex looked very familiar to the reptilian one.

It should be possible to rig up a shark in captivity with harness containing a robotic arm which can be manipulated safely to explore a sharks biting reflex stimuli and figure out if we can put them into a state of temporary lockjaw as well.

Since sharks can not stop swimming, they should not become completely paralyzed like the lizards and my daughter thinks that we would be able to safely ride them.

Taking this a step further, maybe Pavlov's tricks could work on dog-fish too. If the sharks were conditioned to a tone before each snout manipulation it may be possible to train them.