So i have a large pond on a farm. If anything happens id like to be able to go down, get some water and purify for use in home.
Have well water now, the spring feeds the pond. I mention the farm thing bc of fertilizers and other potential runoff. We dont drink our home water rn but use it for brushing teeth and ice cubes. Its been tested and isnt bad but has some turbidity so its not aesthetically appealing.
You need one big stainless steel pot, the kind restaurants use for refried beans or soups, 5-10 gallon. You want these instead of plastic so that you can boil it. Large kitchen strainers for pond scum, a small aquarium skimmer to follow up once it's in the pot, then you need water purifying chlorine drops to handle bacteria, and If you have gas burners or propane, you can then boil that water. Run small batches of this water through pitcher filters and it should be 100% drinkable, probably better than tap water too.
Double boil it for using with powder mixes or contact lenses
I'd also start IDing what fish and reptiles/amphibians inhabit your pond. Since it's a natural pond and you probably don't need to worry about chemical waste, there's probably good protein living in there