Has a driftwood elf gone slightly crazy with an electric drill?
Actually the varying holes and tunnels in this driftwood are caused by the Teredo Navis, a ship worm that is adapted to living in submerged timber.
Taking advantage of the honeycomb wood I have carefully hollowed out this log so LED bulbs can be placed inside and illuminate the tunnels left by the Teredo, this casts a subtle glow and creates a lovely focal point to any room.