Wooden log-ship, in the form of a fish, probably early 19th century.

This particular component of a ship's log is called a log-ship or a log-chip. Thrown into the water astern of the moving ship, the log-ship's weighted hanging flap provided enough resistance to pull the log line off the reel. When the line was checked, at the end of a set time, the log-line pulled out of the notch near the fish's tail, and the log-ship could be recovered easily, head-first. This type of log was in use from the mid-sixteenth century until the twentieth century.