I've done what I can to mitigate water coming in the bottom also. It comes in, but is baffled so it stays in the bottom and doesn't splash up unto the propane regulator. Short of adding a floor and making the locker smaller with a vent further up the transom, I don't think there is a way to fix that and still have a functioning vent. The point of it is that I was replacing solenoid valves and the regulator every 6 months of ocean sailing. Once I had to pay $600 to get me one in Indonesia. Another time I wasted nearly a full tank of propane due to a leaking regulator. I now keep multiple spares, but changing them so often is not a solution. A propane locker really needs to be kept dry, and for that reason that locker isn't a very good propane locker. ABYC requires the locker stay dry, and if a surveyor were paying attention would flag a propane tank there as being non-compliant. That said, a surveyor probably wouldn't know that water comes in the bottom, but certainly should check for a gasket on the lid.What is the sense of a watertight gasket when the locker is open at the bottom and fills with water when the boat squats? If the locker is not used to store propane, then it can be sealed both top and bottom.