The reason why some things are better to fall on than others is because of how fast the momentum is reduced. Force can also be written as the 'rate of change of momentum', which means force is inversely proportional to the time period it is applied for.
In other words, if your momentum is reduced from a very high number (something you'd expect if you're falling from a plane) to zero INSTANTANEOUSLY, the impact force would be extremely large. But if the momentum is reduced gradually by slowing down your descent bit-by-bit, the time period would be longer and consequently the impact force would be smaller, and that's exactly what makes some things better to fall on.
The fallacy in your comparison between 'land' and 'water' is that land is not a homogenous material. Land consists of trees, snow, stacks of hay et cetera, and all these things would be your best bet to land on if you're falling from such a great height, precisely because of the reason stated above - they slow your descent down bit-by-bit.
Water, on the other hand, is infamous for being incompressible. That means if you impact with water from such a large height, instead of giving way, it just halts your descent instantly, resulting in a very large impact force. One general misconception (which you too have fallen for) is that 'land is harder than water'. Even though that may be the case for smaller heights, for larger heights, falling on water basically means death because of the reasons stated above.
It's not just water, though. Any practically-incompressible liquid/solid would act the same. For example, if you (for some reason) decide to land on concrete, it would equal the same amount of devastation as water.
So yeah. Remember all this the next time you're falling out of a plane and your parachute fails.
(If you still have any doubts, feel free to ask!)