A water site is a site that provides one or more water affinity. If a site provides water affinity and other types of affinity (e.g. earth), it's still a water site (and not a land site).
If a site previously provided water affinity and then stops providing water affinity, then it also stops being a water site.
"Land site" and "water site" are mutually exclusive. A site cannot be both a water site and a land site; it will always be one or the other.