Anyway... My subs have gotten wet before and didn't effect them in anyway, just made the box smell like mildew. I wouldn't go testing them though while their wet.
MDF disintegrates when it gets wet. It will also bow and warp easily. subs.. well, if you're talking rubber surrounds and poly or metal cones, not much problem getting wet on the front of the subs. if they're paper cones and foam surrounds, they can incur damage. If the back side of the sub gets wet, you'll get water down around the coils and the motor, and if it rusts, or shorts, you have serious problems.