You're lucky, we adopted our GSD when she was 2 and tried to give her a bath the first weekend we had her (she was a rescue and smelled terrible!). We didn't know yet of her aversion to water and gave up pretty quickly so not to traumatize her after having gone through so many recent changes in her life. Now she goes exclusively to a groomer for her baths and is wonderful with them. She doesn't need more than a handful of baths every year so it's worth the expense.
Our puppymutt, on the other hand, is more like yours - unfazed by water/mud/puddles but hates a bath. I can bathe him myself (he's 50 pounds and much easier to wrangle in a tub than our GSD!) and for his first few months he'd howl miserably in my face during the entire duration of bath time. While annoying, it was absolutely hysterical. He no longer howls but hops out of the tub at every opportunity. He loves the towel-off followed by in-house zoomies.