In general, German Shepherds do not like water. However, it is a breed-specific trait. Dog trainers at the Long Island Central Bark dog training academy recommend mixing a little bit of cheese in with his dinner if you want to coax him into going outside and getting wet. He will be less likely to feel uncomfortable about being filthy or wet if he's also happy or full."
It might take some time for your German Shepherd to get used to taking splashes from things other than pools. In theory, as long as your pup experiences different sensations from those that annoy him there's no reason why he would have any objections...