The Dahlberg Diver would have to be my all time favorite fly. Anything that swims and feeds off the surface of the water will be tempted by the Dahlberg. Murray cod, bass, golden perch, saratoga, barrumundi, even turtles and water dragons love this fly.
There are a number of pattern variations of this fly and so it can be tied to imitate a frog, insect, lizard, fish or even a mouse struggling on the water. Retrieving with short sharp strips causes the fly to bloop, leaving a bubble trail in it’s wake. Another retrieve that works well with bass is to just leave the fly sit in one place. Every now and then a little shake of the rod tip causes the fly to vibrate like a cicada caught in the surface tension of the water.
The Dahlberg also has a very good hook up rate. When fish strike surface flies tied with foam, the fly will often bounce away from the fish and fails to hook up. The Dahlberg is made of deer hair which tends to stick to the water and is less buoyant than foam. I believe this helps ensure the fly enters the fishes mouth.