I have a 98 Wellcraft 240 SE?

I am getting water (quite a bit) in the aft cabin. This is above the water line and only comes in while under way. I thought it was from a 3 hour trip in very rough seas where I was getting totally drenched by the water crashing over the bow, but I have since let it dry for a week at the dock. When I went out for a short time Saturday there was almost an inch of water in the aft cabin. I am completely baffled as to where or how this water is coming in. One thought, is that from the rough trip I took, the water got trapped somewhere and then when I went out again it leaked in cabin, but again, I have know idea even where it could be trapped and the water is sea water. Any ideas will be helpful, I'm thinking of taking it out of the water to look at the hull, but that is a chore and a half, plus if the hull was cracked, I'd be getting water in the bilge. (bilge is dry).. Thank you,