The pike/musky guys have been using deer hair bugs, particulary divers on sinking lines for quite a while. Works really well for bass, too. I like to use froggy type patterns The diving and rising action is just as enticing below the surface as it is up top. Floating flies on sinking lines is also a good way to keep a fly suspended just above submerged weed beds, chunk rock, or other structure that otherwise eats flies faster than fish do.