If a person finds, gathers or catches moveable things which are not already owned or possessed by another person, with the intention of owning them, then the person taking possession becomes the owner. As well as driftwood, this covers things like wild animals and birds, fish caught in the sea or rivers, etc.
If a person takes possession of a thing that is not already owned or possessed by another person, but does not intend to own it, then they become the possessor of that thing, but not the owner.
Whether or not a particular thing is already owned or possessed by another person is a question of fact, to be determined in the circumstances of each case. In the present case, it is likely that the driftwood Albert has found is neither owned nor possessed by anyone else, and he will become the owner of it when he collects it.