regarding water getting into the diffs, gearbox, transfer case etc....if oil can get out water can get in....added to this is the heat vs sudden cooling of water. Unless you drive out your driveway and cross a creek or have come to a stop and let your vehicle cool (think 1hr or more of cool time) all the running gear will be much hotter than the water temp...knowing landrovers and reading through here, you will get an appreciation of how hot the likes of the gearbox and especially the lt230 transfer case get....dunk these hot metal/alloy masses in a large body of water and things change quickly...some quicker than others.
so dont think you have to be parked in the creek eating lunch or wading through 2 meters of water for h20 to get into your running gear....

