[yabbadabbadoo]

2. Under heavy sedation, a single kick isn't enough - it has to be a series of synchronous kicks from the current level and the level(s) above. This is why the rest of the team doesn't wake up either when the van hits the barrier (the first kick), not just Arthur.

[pak]

But Arthur's level at that point is the hotel level; he never goes any deeper. He is at the exact same level when the second kick of hitting the water occurs, and for some reason that one wakes him up. He wouldn't experience any of the deeper kicks because he is not asleep in the hotel level, he is setting up all the explosives on the elevator.