Being a duck hunter and hunting a lot of woodies, I am pretty adept at holding just a tiny bit high and water whacking cripples at pretty close ranges. Don't want to ruin the meat. Actually killed a Can swimming about a foot underwater once. It was a pretty steep angle and I had to try it.
I could have shot at one at about 6 steps but he was angling away and I just let him get to about 15 before I shot. Also killed one at about 10 steps and he had seen something he did not like. Both snuck in quiet. I like to shoot about 30.