They make small plastic screw in pressure relief plugs to relieve pressure in sandwich constructed Sailboards/Windsurfers...they have been around for decades...all you would have to do is drill a hole and bed it with epoxy/cabosil...I have one in all my windsurf boards as well as in my Wave ski (surf kayak) ...anything you make out of open cell Styrofoam (surf board/paddle board/wave ski/sailboard, etc) uses one of these vents. fiberglasssupplycom has them…look in product catalog>Surfboard, sailboard and Kiteboard components…scroll down towards the bottom just after the Sailboard mast boxes…they are listed at $1.77 each…easy to install and work great. They are only 1” in diameter and water tight so you can put it just about anywhere.

Regards,
Robert