Abstract: A bath which has walls making a bottom and sides upwardly extending therefrom. At least one pair of injectors are either continuously mechanically reciprocating or sequentially actuated in a straight line so that fluid jets be moving in order to obtain jets repeatedly continuously displaced as straight lines, along one of these walls being perforated. This bath aims at body treatments, for instance overcoming body pains, particularly the self-relief of aching back. A method is also described for a bath having fluid injectors equally and symmetrically disposed about a median, in two rows, each row being parallel to the median, adjacent to, but short thereof, and parallel to the wall with the longitudinal opening, with the fluid injectors producing uniform fluid jets on each of the two rows, each jet having a uniform trajectory, displacing the trajectory from fluid jets, along two straight lines running across the trajectory, while maintaining spacing between the lines within 4.5.+-.