Assuming it's not fake.

It does seem a bit fake 'cause the launch upward would require a lot more push than the mere downhill slide.

source

There isn't anything wrong with the physics of the launch (PE = mgh, KE = 0.5mv^2, V = at).

I think its fake because there are so many factors that go into the system.  From the video it appears that they used a dummy with the same mass and size as the person to test the experiment, but even then there are many factors (namely wind and friction) that are going to make a big difference from trial to trial over such a large distance.

It seems a bit fake to me since the the downhill slide didn't seem like it could produce enough force/speed to launch an adult in the air like that.

Maybe move the pool closer and i'll settle :)
Still be fun to try.

That's impossible... you can't get a straight line from sliding down from a slide that size... any little movement would alter your angle when launching so that you would miss the water... still a nice edited video!