This is a form of "tonic immobility" in sharks (chickens have the same reaction if held whilst looking at a line drawn away from them)
It's an attempt to feign death / stand immobile whilst danger passes.
Its effective in sharks as they need water passing over their gills so if they stop swimming they are dependant on current.
Of course orcas are big enough to turn a shark over - your average guy in a chain mail suit tries this with Jaws' older brother and it's three months of trying to get steel rings out of your teeth
It's an attempt to feign death / stand immobile whilst danger passes.
Its effective in sharks as they need water passing over their gills so if they stop swimming they are dependant on current.
Of course orcas are big enough to turn a shark over - your average guy in a chain mail suit tries this with Jaws' older brother and it's three months of trying to get steel rings out of your teeth