The majority of the school has gone by, the fly not placed very well, and the guide wants to give it another shot. I would hate to admit the actual number of instances when I've done it, and realized that some stubborn fish was chasing the fly at break neck speed as it was lifted from the water. A few infamous tarpon spots are occasionally populated with large, rapidly moving schools. One requirement in tarpon union rules, is such spots feature nearly impossible visibility. Roller focus creates serious problems in these spots as the fish typically move at right angles to the boat after bumping into it.
Flies thrown at right angles are difficult for the fish to eat, even if they wanted to.
As the fly is stripped it ends up over the back of the next fish in the school. Hungry tarpon can't get to the fly. Boat teams often agree after a day of calmly discussing where the fly should have be thrown, not to fish those spots again. Success depends on blind faith in the guides judgment to throw the fly at a better angle to the unseen fish, fish the guide strangely sees. Of course the guide sees the fish because looking is all he has to do.