The hump sits over the thoracic vertebrae and is built largely from the rhomboideus muscle enlarged and infiltrated with fat. It functions as an energy reserve in lean seasons and as a visual signal, but it holds no water. The camel comparison that produced the water myth does not apply, and the camel's hump is fat rather than water in any case.
Zebu heat tolerance is a whole-body property. The loose dewlap and enlarged ears increase surface area for radiative and convective loss. Zebu have a higher density of functional sweat glands than taurine cattle and a lower basal metabolic rate, so they generate less internal heat while shedding more of it. Short, pale, reflective hair over pigmented skin reduces solar load while protecting against ultraviolet damage.
They also carry greater resistance to ticks and to some tick-borne diseases, which is why tropical breeding programmes cross zebu into taurine herds. The trade-off is generally slower growth and lower milk yield than specialised European dairy breeds under cool, well-fed conditions.