While not a perfect example, if you look at the picture above, you'll see Kona pushing through the water headed for the bank. He's right of the blind (which is indicated by the orange stake on the bank to his left; it might be easier to see if you enlarge the photo). I'm about to give him sit whistle and left-back cast. I could wait until he hit the bank to do it or wait to see what he'd do when he did hit the bank. The problem, besides losing control, is that those weeds are pretty high and if he gets into them before I hit the whistle and he reacted, he could be deep into them and when he did sit, he wouldn't be able to see me. A come-in whistle would bring him out, but who knows what could happen between that sit and the come-in (especially if he were a young dog); maybe he gets distracted, maybe he winds the blind, maybe he finds another bird or any other number of possibilities. At that point I'd be losing control of the situation and hacking my way through it; teaching him who-knows-what.