Most of the USA.
Anything from 2-5 foot or even longer depending on the water snake species.
Upto 15 years.
24x12x12in for smaller species, 36x18x18in for larger species.
Woodland with a large bowl or even inbuilt water area for soaking. Make sure hides are provided in both the warm end and the cool end.
In the wild water snakes would eat fish and amphibians. In captivity they should be fed fish supplimented with a reptile multi vitamin (pay particular attention to finding a good source of thiamin). You could also try to wean over to scented rodents.