Please be patient with me, a newbie - but why do you caulk this anyway? I opened my tank cover just to have a look around - getting the old caulk out was a pain. I've replaced the cover but haven't recaulked yet. It doesn't seem that that much water can get in, and if it does it just drains to the bilge. I can tell from the thread that I should probably re-caulk, but I wonder how necessary it really is???