Thats an easy one, you have no pool, you have a pond, which will further reduce your cost for insurance in the event of a house fire and water is readily available. Estimate how many gallons are available and the distance from your home and out buildings as the insurance will want to know. Keep the signs and postings up to avoid any conflict of liability. But it should be address as a pond and fresh water source as needed for gardening and emergencys such as fires.
If questions do arise, check with your lawyer and ensure this coincides with local regulations, if any, and your insurnace coverage coincides with your liabilty of the pond. You may wish to have some sort of excape from the pit available should someone fall into the water. It sounds like the fall will not kill them, but drowning would be their fate, cover that angle as well should they get by the fence and can't read english (ladder).
That would be my first approach, as insurance will charge for anything they can get away with, and classifing it as some other than what it is, would be one of those charges. Meet the law,and nothing more, but the ladder may be an additional savior,and prevent any questions in the event of an accident, and perhaps a civil matter.
If you have faith in the agent, you may wish to have him out and push this angle, if he dissagrees, do as they wish and seek legal council for advise to ensure you are not paying for something other than what is mandated by you local laws.
Perhaps a cover is all that is needed for protection and an emergency water source. I have also seen them down south with a barn structure built over them.
