Custom kick panel water shield

[88Stanger]

I have been researching on building a custom set of kick panels, using the existing vent as a baffle, but with that said, I am concerned about getting water on the speaker itself and have read about "Water Shield". Curious as to what exactly this is. I do not want to block out my vent as i want to use the "open Air space" so suggestions how to keep the speakers safe in this area?

I am going with Vintage Air, so the vents will not be used for this.
Thanks for any suggestions ..