re: Fishing etiquette?

I wouldn't worry about it. People that anchor out in the middle of a canal/opening when there is fishing area to be had behind them should expect to be passed by. I had this same problem a month or so ago in the spillway. Some asshat anchored off in the middle of the area I was trolling in (i got out there long before they did) about 150 yards from the end of the cut we were in. I went all the way to the bank to go around him and I hear him talking shite under his breath to his buddy. I asked quite nicely twice if I was bothering them but he never responded directly to me, just mumbling to his buddy to where I could hear. If you got the nuts to attempt to block off several people from fishing the area you were late getting to, at least have the nuts to back it up when asked about it.