which lake ? Are you talking "Muddy Creek" on Watts Bar Lake ?
Fall Crappie fishing results depends on which species of Crappie you are after. White Crappie tend to hang out in deep water, around submerged brush piles and/or along channels with wood cover, or suspended above deep water structure and under Shad schools. Black Crappie tend to come into the creeks and bays, following the Shad as they migrate into the backs of creeks. They tend to use deep water docks as ambush points, and timber (if close to the bank, on deep banks).
"Deep" is a relative term ... but, to clarify - in reference to White Crappie, deep is the 20ft and deeper water. For Black Crappie - deep means less than 20ft, but generally deeper than 8ft of water depth (from surface to bottom).
The cooling water temps and clearing of the water, during the Fall to Winter transition, is more to the liking of the Black Crappie. White Crappie prefer warmer water, and more stained/murky water clarities. But, they seem to be willing to sacrifice the warmer water conditions, for the security of the darker depths.
I'd look for some submerged timber or brush piles ... in the 15-25ft depth range. I'd also start 'shooting docks' ... esp those with 15ft or more of water depth under them. They should be around the same areas & deep cover, that they would generally be around at the pre-spawn period. Look for them to be in the upper half of the water depths, if there's shade on the water above .... in the lower half (and around the submerged timber), if not.
There's no guarantee that any of this info is correct, or pertains to your waters. It is just what I've observed from fishing Watts Bar, in the Fall tournaments, over the last 5 yrs ... and the results of most of the top finishers in those tournaments. Shooting jigs under docks seemed to be the most successful method used by these anglers (mid Oct time frame) ... but, don't discount a lively 2-3" minnow or Shad, on a hook/sinker/float rig. Successful "colors" change too often, to mention any one as "the" color of choice ... but, a "hint" of Chartreuse, to a full 1/2 of the jig body being Chartreuse ... has proven to be a successful color choice. .....luck2ya ...cp