I agree with Chiron's idea. How much has the texture and the appearance of the wood changed? If it has changed drastically, as Chiron said, it obviously would not encompass the aspects it used to before being changed by the water.
Water itself promotes the emotions, cleansing, change in direction, etc. Take a look how the properties of water have influenced the wood- can the water have passed on similar properties to the wood?
This had me curious myself, so here's what I found through a bit of quick research:
''While each tree celebrates its own unique magickal qualities, when wood becomes enveloped in waters ebb and flow, its original properties and form become altered by the additions of other multiple energies it then encounters. The wood absorbs the new energies from life sources which are also housed within the water.
And too, since it no longer is restrained by roots and earth, within its newfound freedom of travel, woods magickal energy base and form is then continuously enhanced by a multitude of natural forces. Therefore, I believe it is not necessary to know the original source of a driftwoods birthright.''
Again, as Chiron also said, driftwood itself has it's own representations which you may want to look into.
I'd say that if anything, driftwood, from an aesthetic view point, would make a rather beautiful wand, especially if decorated with shells, sea glass [especially for the tip] , and maybe a sea gull feather. It would be a tool to make Neptune proud, one surging with the elemental powers of water.