car is just sitting (not registered at the moment) and some water collects in drivers side trunk well (where jack is stored). trunk lid gasket looks fine---I'm baffled how water can get in as it just sits there getting rained on...any thoughts (I'd like to avoid getting into the trunk and have someone hose the car down while looking for leaks LOL)

I'm guessing you have a sedan with this answer. Sometimes the sealant used between the taillights and body will dry out and crack. Allowing water to get in.