The Teredo worm (shipworm)has been the bane of wooden ships, boats, pilings and retaining walls since man has ventured to the sea. A type of clam, the Teredo worm has two shells, enclosing only the front end of the body which function as a tool rather than a protective covering – they are a boring clam. Each shell has toothed ridges which shave away bits of wood into smaller pieces and then those are ingested.
Teredo worms have been known to achieve a length of up to 2 ft long, although the shells remain only about a foot long. The British and Spanish navies estimated that a wooden hull in the Carribean in the age of sail would last ten years.
Mariners as early as 500 BC tried to protect their wooden ships by various combinations of arsenic, sulfur, tars and oils. The British Navy experimented with a sacrificial covering of wood covering tar, but it wasn’t successful. It wasn’t until the invention of copper hull plating that the Teredo worm became less of a problem.
I was under the impression that they were more of a problem in warmer waters than we have in the Pacific NW. But apparently they’ve damaged seawalls around here and gnawed on some boats. Yeesh…