flyguys--Obviously depth will depend in considerable measure on the size of the stream. Bigger ones in the Park, such as Little River, lower Luftee, Big Creek, lower Abrams Creek, etc. will have the occasional pool over one's head. On the other hand, I can only think of a half dozen or so pools in all of Deep Creek which have depths of more than six or seven feet--Big Rock, the swimming hole just upstream from it, the Turnaround pool, the big hole in the bend of Bumgardner Bend, and the Hoye Hole come immediately to mind. Deep Creek isn't all that deep.
Once you get above 3,000 feet or so deep pools are quite rare, although the big pool at Three Forks (on Raven Fork)is quite deep.