Unironically, positioning, pressure, and time. It took me a while to be fine with the pressure needed to actually clean anything, let alone letting it stay on long enough to thoroughly clean. Plus you gotta angle yourself so everything gets clean.
Saying “it’s water” proves you don’t know enough, which explains why you’ve had a bad experience. No shame in that, like I said it took me a while. Stick with it, it’s worth it.