Get it in writing - that the 2 adjoining/bordering properties have NO rights or access to the pond. Get it in writing, signed by both property owners, with an inclusion that when they sell or give or gift their property away the recipients have no rights or access, in perpetuity. Authored by an attorney, signed by all parties, and notarized.
That is of course if their property line actually touches the pond or is within 25 feet.
