Studies in humans have found that water temperature influenced intake, with cold water preferred over warm or hot water (Boulze et al. 1983). However, a study in dogs comparing tap water at 4oC, 24oC and 40oC (Homes et al. 1960) found no significant effect of water temperature.
Temperatures below 50 degrees could be problematic, especially for certain dogs (see breed section, below). However, length of time swimming is also a major factor. A quick dip or splash in a cold body of water isn't likely to cause a problem for an otherwise healthy dog, especially if you dry them off afterward.
Drinking water should always be available; the amount a dog needs depends upon the weight, health status, and environmental temperature.
Water for drinking is also a very important part of your dog's daily. Water also serves to cool the body down and works to maintain a normal body temperature.