Thanks for the response, I cant fill it for this is where all the wires and hoses run into a 4" conduit up to the front of the boat. This well is right under the drain hole in the rear of the cockpit, maybe the drain hole has a small leak in it.
My 97 has done that since day one,i traced it down to when you wash the deck or it rains the water seeps through that access door,if mine stars to stink i spray some fresh water in there,if you run some ruff water it tends to splash most of it out.If you wanted to you can get a can of Great Stuff foam gap sealer and fill that valley,i was gonna do that once but life happens and never got to it