There is an error in your descriptive, which I find inaccurate, pg. The intent of waterboarding is not death, it is something else inspired by the fear or death by drowning. Drowning includes death, does it not? If you don't die, you didn't drown.
If you consider that drowning means death, then it would not be drowning. Then again, it wouldn't be "simulated drowning" either, as it is usually described, because you aren't simulating death, so that would be wrong, too.
Regardless, it most certainly involves filling the lungs with water, which is part of the process of drowning (drowning can be more complicated). The important thing to note is that this is not just making a person feel like they drowning, it involves taking them through the actually physical processes and causing the same reflexive responses. The only thing they do is to stop before death occurs (prolonged waterboarding (how long?) will lead to death)
OTOH, I'm not sure the idea that drowning = death is correct, at least in common usage. For example, how do you describe a person who is sunk to the bottom of the pool? When people are flailing in the water, what do they scream? "Help me, I'm drowning!" "Help him, he's drowning"
It seems to me that "drowning" refers to the process of dying by water inhalation. "Drowned" is when they are dead. I'm trying to think of an analogy, but can't come up with one, though.