Originally Posted by
A0283
I have not had time to think about what kind of aerodynamic forces would shape this 'hand'.
For my money, your second point on "hydrodymanic forces" is a good avenue of inquiry.
Such a twisting might be the result of a rotating body not hitting the water's surface in a more or less "flat" attitude (as did AF 447) but rather in a more or less "tilted" attitude.
It might not need to rotating to get a tear like that if it has sufficient ground speed and tilt, depending on the vertical velocity at impact as compared to lateral / horizontal velocity.