Last summer, I placed three floating targets on a lake at 200m (219yards), 400m (437yards) and even 800m (875 yards).
I got the idea when I was placing my fishing nets.. With a GPS in my pocket, I placed them so that they where in the right distance up towards a hill and had a totaly safe background (+ left and right side of the targets).
I tried the targets with my arty, and where amazed over how close I actually hit at those ranges! I shot mostly one handed without the stock, it reminded me of throwing rocks towards a stick as a kid.. wich abviosly still is great fun
With unlimited time and 9mm rounds.. anything is possible
The water was very still.. so it was easy to spot the impact some two/three seconds later at 800m.
But shooting towards water like this can be a somewhat spooky, the bullets can reflect into some weird angels and still have enough punch in them to cause damage. So a totaly safe background is needed for this type of fun.