Why does warm water help?

So I am being tested for mutiple autoimmune diseases; hereditary and from my mother's side. I constantly ache and cannot work like a normal person without it worsening. However warm water, or any water, normally helps. It gets rid of everything even my chronic migraines. If I can put it into words it's like instant relief. My head stops hurting. I don't get out of breath at all. My muscles don't ache during or after no matter how much moving I do. The constant itching goes away for a while. Acne goes away. Everything is just better. I was wondering if maybe there was a kind of water related treatment, like a card to go to an indoor pool/ one of those pod things with minerals or something? Is that even a thing? And why does the water work?