Riparian rights, and the manner in which property lines extend into a body of water (if at all) depend upon the jurisdiction. Sometimes, the location of the natural shoreline is key to determining boundaries. Sometimes, a lake is carved up like a pie, with property lines extending to a center point.Quoting admanb
While ordinarily a conveyance of real property must be in writing, that may change based upon the actual construction of the dock, depending upon the local law.Quoting admanb
A survey may resolve the issue. Beyond that, if the neighbor won't listen to reason, you may have to litigate. You may wish to discuss this situation with an area real estate lawyer, such that you can determine what rights you have if a survey shows the dock to be encroaching on the neighbor's property, and what a court might order in such an event (e.g., will the court order payment of some amount of compensation for a "trespass", grant an easement, order the removal of the encroaching portion of the dock, or order some other form of relief?)Quoting admanb

