An irregular ongoing series of interesting facts related to boating.

Toredo Worm:

The Toredo worm (ship worm)has been the bane of wooden ships, boats,
pilings and retaining walls since man has ventured to the sea. A type of
clam, the Toredo 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. Toredo 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 was 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 Toredo worm became less of a problem.