I do a lot of cutting of old, downed wood. Sometimes you can get something out of it...sometimes not. You might just have to open the log up a bit and take a look. I would suspect that there will be some...maybe a lot of damage. I do manage to salvage cedar, juniper, and mesquite logs quite often. The logs hiddern under water are a different situation. Lack of oxygen protects the wood in that case. If it is fine, old growth wood it could then fetch a PREMIUM price. Probably better than panning for gold.