I've took my boat out of the water for the winter and was cleaning it out below the deck . When cleaning l could smell something really bad coming from the drain holes which lead into the bilges of the boat which is double skinned . There is a lot of brown polysterine stuff in there which also feels damp.I managed to get a flat screw driver in there and scrape a bit out. I have put the bow as high up as l can to try and make any water run out but there's nothing coming out ??. Which could mean that a bit of water might be trapped in there.. Any ideas ??