Genuine I reckon.
The shadows, reflections, smoke and plumes all point to it being real. Everythings in the right place, with the right lighting.
It could be faked, but it would take a lot of time and money to do. At least as much as doing it for real. You'd have to fly the ac as close as possible to the water and film them. Then rig up some way of producing the appropriate wakes and plumes and smoke, at the same speed as the ac, and film that from the same relative position as the ac. Then composite it all together seamlessly, moving the ac down to where the plumes/wakes are, and remove all the rigging, plus rigging shadow and reflections. Nightmare job. Weeks of work in a top notch facility. Mega bucks.
I'm a Photoshop veteren, and I do video and 3D animation and compositing.
Theres no point looking at jpeg compressed images for signs of fakery, jpeg compression produces its own edge and 'halo' effects and would cover up any original 'fake' effects.
I also reckon, though I've never tried, that the water would push back at that speed and provide quite some resistance.
If it did dig in, the end would be pretty quick though.
SimonHK