Hollow wood paddleboards require a vent so they can equalize the internal pressures. I recommend using a screw vent as they work flawlessly, are really easy to install, and most importantly, they provide an audible check every time you open them.
The easiest way I know for testing if a board is air/water tight before it leaves the shop is to breath into it the vent to pressurize the board and tighten the vent. The next morning when you open the vent you will hear the pressure equalize. This test is done every time you use the board by simply listening as you open the vent. You can hear the internal pressure equalize!
NEVER leave an unused board in the sun with the vent closed, use and air compressor, Shop Vacuum, or other mechanical devise to test if your board holds pressure. Wooden boards are designed to be waterproof not to hold high pressures.
