I apologize for the word wrap in the prior posting. I hope that this one is correct. Outer Reef, a 36 trawler with sails, has a sea chest. The sea chest is 13" D X 26" L X 24" H. The bottom of the chest is the boats hull. There are 66 holes 7/16" in diameter, in 6 rows each with 11 holes, drilled through the hull. All sea cocks , except the air conditioning sea cock, come out of the top cover of the sea chest. Each has a PVC pipe that extends from the top of the chest to the bottom of the chest, almost touching the bottom. The a/c sea cock comes off the side of the chest. The water line is about 6" below the top of the chest. There is an access plate on the top of the chest that provides access inside. I am not sure about a vent. I had never thought about the need for a vent and had never looked for one until this discussion on T&T. If there is one, it has to be a part of a deck washdown system supplied by a pump on the generator. The sea chest provides saa water for the main engine, generator, water maker, aft head, a/c, and wash down system. The forward head and depth sounder are the only underwater thru holes. Larry Outer Reef Port Aransas, Texas