Who owns the water when a property line shared by two owners runs through a private pond?

As a rule, water isn't owned when it's in a moving body such as a stream or river or in a pond lying across property lines. Even though the property lines often extend into the water, the ownership rights include the stream bed or the floor of the pond but not the water within them Water is generally a "usufruct" (from the Latin "usus" and "fructus", literally meaning "use of the fruits') and is therefore a shared right of use. In other words, an owner whose property line extends into a pond have the right to use the water, but not to do so in such a way that deprives the other owner of the right of use.