My 1975 Cat-22 seems to have a "sealed-at-inner-top" compartment on the starboard, and a not-sealed one on the port side. It is so rough up there that it looked like a sloppy job, so I sealed it with silicone after it allowed water to enter the hull when heeled over a bit too far. Aldo, I really didn't want to heel that far, but in the spirit of competition (Wyoming's "Little Americas Cup"), had a bit much sail for the thunderstorm that came up before the first buoy after a near-calm start. Incidentally, my old boat has only one air vent, and it faces backwards which is good for over-heeling though not Coast Guard approved by today's standards. I avoid carrying gasoline below, but wonder if there is some other way to get a forward facing vent that won't ship-on unwanted water?