Not sure what you have under yours as a partial 3rd log, but here's a shot under our Party Cruiser. Note the partial log in the back. Also note (look hard) the M bracket. Note it's solid from front to back, and it's wide open towards the front. The back of the log, and M bracket, are butted up against the transom... so guess what happened while underway? The M bracket makes a perfect water scoop, and once the water hits the transom, it wants to get OUT. And if you opened the battery box door under the bed in back while underway, you were treated to an upside-down wall-of-water! The water literally shot straight up and onto the floor! Just driving the boat would soak the back carpet...Everybody with one of these knows what I'm talking about!
The fix was simple, I just filled up the M bracket space with spray foam and sawed it off flush
-- never had a wet floor again!
SO, whether you have a setup like mine or not, I don't know, but ANYTHING under there in the middle can cause water to spray upwards, and that'll end up in your boat...