IMO it should be ok.. I'd take the screw out and let it dry.. These cores don't soak up water and I can't imagine much getting past the threads of the screw.. Maybe stuff a rolled up paper towel or tissue into the hole to try and wick any moisture out.. I'd also be resting the board upside down.. Fingers crossed..

If the water is colder than the air, you run the risk of the board cooling when put in the water, and sucking air through the vent... and any water that submerges the board

But after some time, the board should be at the same temp as the water and limit the water entry.

To be sure, like DJ said, let it upside down under the sun and see if water drips. And weight the board, to be sure.

riverider said..
can't understand why some of the manufactures still aren't using the self regulating gortex vents in their boards ?

I guess:
- price
- fear of failure (but it does seem to stand the test of time)
- fear of user messing with it and breaking it (now, this happens quite often)
- fear of the theoretical issue of water in vapor form (not mist which are water droplets in the air, but water as a gaz) going through the vent (gortetex blocks the water but not the vapor), and condensing as water in the foam blank where it can accumulate between the beads and get stuck by capillarity. But I didn't read that this actually happens in real life.