How much water is too much,

[LanceS13]

The bypass valve is vacuum actuated.  Atmospheric and positive pressure keep it closed.  It does open and close, so it is a valve.  The only way it will work is if the entire cross-sectional area of the intake track is blocked by water, creating a vacuum as the air in front of the water is sucked into the engine faster than the water can be pulled up the intake track.  This can only happen if the entire filter is submerged.  So unless your car is an amphibious vehicle, the bypass valve is a useless restriction IMHO.

And if you think about it, the compressed volume of the chamber probably isn't much more than a teaspoon.  But you still have to suck up alot of water to get that much in there during a single piston stroke.