Hydrotherapy (aka heat treatment) is depicted as being painful and barbaric, with water heated or cooled to intolerable temperatures. In fact psychiatric institutes were careful to keep the temperatures at a reasonable hot bath/cool bath level, specifically to make them relaxing.
In respect to the ongoing excellent attention to period detail, in the restaurant scene with Nurse Ratched and Dr Hanover overlooking the ocean the window frames are clearly inaccurate to the period. Extensive searches of late 1940s historical photographs of Californian ocean view restaurants always yield wooden window frames, not metal.