"Carpenter fish" is an archaic, obsolete term that pre-20th century mariners ascribed to the hypothesized species of fish they imagined were responsible for the strange tapping sounds they could hear through the wooden hulls of their ships, which sounded like a hammer pounding a nail into wood. It is now known that these sounds were actually the echolocation clicks produced by sperm whales. US Navy sonar operators still use the term colloquially.
References
Carpenter fish Wikipedia(Text) CC BY-SA