As one of my jobs it is to handle crisis in the City I work for and recently there was a park that had a collapse due to these worm-like creatures called "Teredos" which are considered to be the sea termites.
Because Teredos, aka shipworms, are clams. The adult body is worm-elongate and the shell is reduced to a pair of corrugated, crenelated rasps at the business end of the beast. They tunnel through wood but feed in the ordinary clam way by filtering water drawn through a siphon. The wood is shelter rather than food. Since they don't actually consume the wood they bore through, preservatives like creosote mainly hinder only the colonizing larvae.
Interestingly they somehow percieve the presence of other shipworm tunnels and the limits of the wood -including bolts, nails, etc.- and avoid them. Thus, even though an individual shipworm's tunnel may be convoluted and tortuous, it is nowhere breached and is open to the outside only at the site of initial penetration. There are a number of different species, with the ones of most economic significance having been transported worldwide long ago via the worm-riddled hulls of wooden ships.
via Majikthise
