Teun & Katrien: Installation of a robotic lawnmower with a ditch/pond
Since a ditch/pond often has a slope / sloping piece of land, it is wise to fence it off with, for example, an edging. See as an example; https://www.kunststofreus.nl/borderrand.html
The robotic lawnmower will stay within the boundary wire, but can slip in wet weather and end up in the water.