If your brave you can fill a spray bottle with water and spray a mist over all the wires in the engine compartment. If you have a bad wire it will arc or cause the jeep to run rough (you will hear a crack when the arc goes to ground). Beware though this could cause a spike in the electrical systems, but I would think no more then running it through a car wash. Check all your engine sensors, particularly the ones on or around the engine, for water damage or burn marks/soot buildup as this also could be causing this. Another possibility it that you have a cracked or disconnected vacuum line. If this happened it could suck up water into the intake and essentially kill the jeep. If too much water ends up in the combustion chamber you could end up hydro-locked also (definitely not a good thing). There is something wrong, and the Jeep should not die out when running through water, that is, unless it is submerged in deep water without a snorkel.