You need to check laws in your state, but in many, the landowner owns the land, but NOT the water. So if they have legal access to the water they would have access to all the pond as long as they stayed in the water.
http://www.tba.org/news/tennessee-water-laws-and-regulationsIII. Tennessee: Surface Water and Groundwater Supply, Ownership, Use, Rights, Regulation and Permitting
A. Water Property, Use Rights, and Public Interest
Before you can address permits and filings for securing a water supply in Tennessee, you need to consider property ownership and rights of use for any water resource.
1. Most Tennesseans believe that they own the water on and under their fee-owned land, and that this right comes with land ownership.
2. But in fact, the state claims ownership of all waters of Tennessee in the "public trust," including the groundwater, unless the water body is isolated and confined to a single private property. See TENN. CODE ANN. §§ 68-221-702, 69-3-102(a), and 69-3-103. Historically the beds of navigable watercourses are also owned by the state in trust. But landowners can own the beds of non-navigable streams, and landowners' water use rights in either case are very strong in Tennessee even though they are deemed "incomplete and incorporeal."
