Unless you're in a place where you're limited to one fly, use two. The top one will be for bouncing on top of the water; an elk hair caddis might be a good choice, or some sort of wet. Use a bulk wet as the bottom fly. Put at least feet of tippet between the flies. Get above a rising fish, with just enough line out to reach it. When the fly reaches the fish, lift the rod tip and raise the top fly out of the water -- the bottom fly acts as an anchor allowing you to do this. "Bounce" the fly by lowering and raising the rod tip.

I do this trick as a last resort in the situation you describe, and it almost always works.