On the youth duck hunt this past weekend I pulled out the range finder to establish a reasonable shooting perimeter for my young hunter. We had our backs to a dike with marsh/salt grass with scattered ponds in front of us. I was very surprised how close 40 yards seemed. I then realized there was nothing within my frame of reference for my eye/brain to latch onto to compare size and calculate distance. The dilemma was even more apparent when a huge goose flew over. Because he was soooo much larger than the ducks we had been watching, he appeared closer than he actually was. Now this was my first time in the marsh so I am a newbie, but what do you all do to accurately judge distances in that environment?