I've found driftwood in rivers/creeks and used in in my tank many times, aslong as it isn't cedar, since sometimes that wood can put harmful toxins into the water. Cedar has a distinctive smell, so it is easy to tell if it is cedar or not. Before putting the driftwood in the tank, I rinsed it very and a brushed of all debris, as well as make sure the wood is not soft in an area (if it has a soft area, this means it will have a higher tendency to rot in the future). Then I boiled a few time, and put it through the dishwasher (with of course no dishwasher soap) and that cleaned it very well. I placed it in my tank after that with rock weights and it takes a very long time for the pieces to become water logged, sometimes a year IME. Don't worry if the pieces release some tannins into the water, as this is not harmful to the fish as long as it is not too much.
Good luck!
Matt