Trees and shit are "natural" and wash ashore all the time... processed lumber ain't, and is usually removed when found.
Gary
The first time I came out west and walked along the Pacific shore somewhere just south of Crescent city, the amount of driftwood on the beach made a big impression on me.
That was 30 years ago, seem like erosion control works better today, one usually doesn't see so many trees and rootballs washed up.
But then on occasion: