Neither was I, Anthony...
There are many reasons for having large volume "still air boxes" on vehicles, and reduce excessive negative pressure (or "vacuum") at the airbox intake is just one of them. Try this when you get a chance... Fire your engine up, and then reach up in there where the airbox intake is and try and *feel* any "vacuum". No fair covering up the airbox inlet... As the instant you do that the engine will evacuate what air is in the airbox and fairly quickly produce a felt "vacuum". No, just see if you can actually feel the air being drawn into the airbox.
Better yet, fire up a good cigar... Get it smoking really well, and see just move it around in front of the motorcycle to see how much "vacuum" there is. Move it closer and closer to where the airbox inlet is and you'll quickly see how close you have to get before the smoke really starts moving toward that intake. You might be surprised at just how little "vacuum" there is until you get pretty close.
As far as intake height goes... The only height important in this instance is the lowest edge of the rubber intake trumpets up inside the airbox. That's how high the water would have to get before the engine could start drawing in enough water volume to start causing problems like hydraulic lock. To get there the water would have to get past the air filter (which is harder for it to do with the stock paper filter than it is with an aftermarket oiled-gauze element, BTW), then fill up a rather substantial portion of what is a pretty high volume (5 to 7 liters I'd guess, if not more) airbox.
As I said, IMHO I think you'd have to be in some very, very deep water for a relatively long, long time for this to happen.
Just my two centavos... YMMV, or should I say YDMV...
Dallara
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