Whats it called and where did you get from?
I had to ventilate to get past coastguard inspection.
So put a round hose vent(exactly where your shows actually) with louvres on the front.
Then on the rigid hose coupler on the back I cemented a 90 degree elbow up and a 6" length of pipe with a couple of angled baffles set in it.
It wont stop a complete deck swamping but would fend off any splash or anything under about a foot of water in the boat.
But I do like yours if I were to go offshore.