What is indicated by the 17 mark on the lead line?

The 17 mark on the lead line indicates that a red rag is being used. In maritime practice, lead lines are used to measure the depth of water and provide information about the underwater features of the seabed. The colors of the rags are significant because they correspond to specific depths or obstructions.

A red rag specifically denotes the 17-fathom mark, representing a significant depth that helps mariners to ascertain their water clearance and avoid running aground or encountering underwater hazards. Understanding these markings is crucial for safe navigation and operational planning on the water.

While the other colors denote different depths or warnings, the red rag holds specific meaning in terms of depth measurement, making it essential for navigation and safe marine operations.