The previous owner of my previous Bavaria (2000 B31) had “teak drain channel strips” made and fitted at an angle above the vents. This meant that rain or spray water flowing back along the channels beside the sliding hatch cover ran onto these teak strips and then into the cockpit instead of down onto the air vents.
Although the vent slats are angled down, strong wind can blow any water which is on the vents through the slats.
I have photos but haven’t been able to include photos on the forum when I’ve tried before. If you send me a pm with your email address I’ll send them to you direct by email.