Mineral springs spas specialize in hydrotherapy, with waters that have trace elements that benefit for the body. The exact makeup of the water vares from spring to spring, and different waters are considered beneficial for different ailments. They may offers individual baths, communal pools, or both.
Not all spas offer hydrotherapy treatments. The bigger and more elaborate the spa, the more likely it is to offer some form of hydrotherapy. One of my favorites is a Vichy shower, which usually follows a scrub and/or body wrap. You basically get a shower with five or seven heads while you're laying down.
Some body treatments involve rinsing off in a vertical shower with lots of shower heads installed, so that water comes at you from different directions. This feels pretty good, but the pressure has to be good and the heads well positioned so it doesn't splash into your face. In Europe, you might stand in an open shower and have the therapist hose you off gently.