bypass valve?

i was wondering if any of you could explain how a bypass valve works, i know it is to prevent the engine from gettin water through the intake but just how exactly does it do that because when i look at mine i dont understand how a piece of foam and plastic does such a thing, i have done all the work on my car and i am pretty good at engine knowledge just dont understand this part:smoka:

From what I gather off AEM's website, the bypass is pressure sensitive. When the filter is submerged in water, the engine pulls way more vacuum then normal because water is harder to suck up than air. When this happens a screen of somesort on the bypass opens and allows the engine to run off of unfiltered air. Thus avoiding hydrolock.

That's what I've pieced together.

that is exactly right.