Those who know them can pick out our friends who were the stunt men in certain clips but the actors did a good bit of their own paddling. Watch closely and see that, once again, the Old Town wood canvas canoe breaks apart in a perfectly sawn straight line even before the Grumman aluminum canoe touches it. That scene was on the Tallulah River.
Except for the big names, most of the bits were played by local folks. Yes, I know Billy, and No, he can't play banjo. Rent the movie.