I originally saw this concept on a Skip Morris pattern (Predator Dragon). I have used it with success. Like a Booby Fly, I put a heavier sinking line on the bottom, which allows the fly to then float up off the bottom. Adjust the length of the leader/tippet to elevate or lower the fly from the bottom. An Intermediate Line could be used in shallower water along the edges or near drops of stillwaters/lakes.

Floating Dragon Fly Nymph (SwittersB)

The body is yarn, not dubbing, although you could dub it or wrap any yarn/chenille for the body.