when oil and water mix you usually get emulsification, in other words, it thickens and forms a creamy coloured substance that is commonly referred to as mayonnaise. gear oils usually turn a lovely shade of grey/brown/cream, depending on the amount of water.
as for the swivels, i usually find that jacking the front up, removing the wheel, and then loosening the top swivel bolts is enough to check for water ingress, as any that has got in usually drips out the bottom. if it does, then it pays to strip and clean the bearings before the get ground to paste.
generally speaking, you can jack a landrover under the diff, or anywhere along the axle. i usually jack under the diff, then support with stands on the outside of the front radius arms.
props are easy enough, get a grease gun and pump the joints full of the stuff, you will usually see some escape the seals when there is enough in there.