You let out some line and it’s perfect cast to the head of the pool. Fish are still gulping everywhere and you’ve lost focus for a split second. In that split second your line is split across two different currents, one moving faster than the other. Now your fly is dragging across the surface, it’s so bad that the wake left behind the fly looks like it’s water skiing across the pool. Fish seem not to notice, they’re still slurping up caddis on the surface as if it had never happened before. Yet, they’re not interested in the waterskiing caddis that you’ve got at the end of your line. And nothing is going to change until you focus on your fly and keep it from dragging through the varying currents of the pool.
I’ve read before that if you can see your fly in one out of a hundred casts you don’t have a problem seeing your fly, i.e., the fly is not too small for your eyes to focus on it, rather it may be an issue with casting. If you can improve your casting and consistently get your fly into the same ten inch area with every cast you will increase your opportunity of seeing your fly when it is in the water.
Keeping your drift drag free and always having an eye on your fly will improve the amount of fish you bring to hand. As always, Good Luck and Guid Luck!