a marine organism that attacks submerged or floating wood structures in salt or brackish waters —note 1. two main groups of marine borers are recognized: (a) crustacean borers (e.g., from the genera Limnoria [gribbles], Chelura, Sphaeroma) and (b) molluscean borers (e.g., from the genera Bankia, Teredo [shipworms], and Martesia) —note 2. Limnoria tunnels just below the wood surface, causing a characteristic deterioration of the timber; Teredo tunnels are generally lined with calcareous material —synonym timber worm This definition last updated 07/14/2008