Speaking of the hole on the forward wall of the cockpit, that is indeed a vent hole, it keeps the pontoon hull from overpressurizing on a warm day, which could pop a seam and/or detach the foam block inside. Don't plug it up (except for a leak test). Also don't let the cockpit fill with water while boat is in storage, water will get into the hull and soak into the foam.
Check along the metal edge trim real well, especially up front where folks ram docks.
Cheers
Clark and Skipper
Signal Charlie