Ans.

There’s nothing terribly special about water, and even hitting a gas fast enough would “feel like concrete”.  For example, when meteors (which are fast) hit the atmosphere they generally shatter immediately. The more energy that’s involved in a collision, the less important the binding energy (the energy required to pull a thing apart) is.  A general, hand-wavy rule of thumb is: if the random kinetic energy of a piece of material is greater than the binding energy, then the material will behave like a fluid.  A bit more energy, and it will fly apart.

So, when you fall from a great height and land in water there’s a bunch of kinetic energy going every which way.  The water continues to behave like water, but since the kinetic energy in different parts of your body are greater than the binding energy keeping them connected, then the body as a whole will act more like a fluid.  That is; it’ll “splash” (in the grossest sense).