If you want real drift wood, If you are near any coasts, it's the place to go... Be sure to be the first after a good storm.
You could be surprised what can be found. Use one of your "illegal" pocket knives to check the hardness of the wood you consider. I live near the st-Laurence in Canada and the nice pieces never remain there for long. Also bring a little axe, in case you find a big tree you can bite off a morsel that be of you liking.
The wood can be boiled, backed, bleached, brushed and soaked for a while. Real drift wood is water cured and once treated are very low in nutrient release and even less in tannin
I only bought wood because it was really stunning and It's difficult to find driftwood that has a very dark color, but lighter kind, came along with great nuances with time, some develops purples and green. The natural look is always winner.