Siberian tree trunk

These tree trunks are found all around the northern coasts of Iceland - in some places there are hundreds of them I found this one a beach in the western fjords. I liked it because of the honeycomb effect caused by marine organisms after years of immersion in the chilly nothern seas. Two pics for this one - one to show its a tree trunk and one a close up of the cellular structure.

Are these fossilised Ross, or just cured by the sea water?

They arent fossilised - the wood has been eroded by years in the sea but the slightly stronger / more robust hexagonal cell edges have survived slightly better. You can break bits off though quite easily, and its definitely plant matter. Its hard to explain and very weird.