What item indicates the 5 mark on a lead line?

The correct indicator for the 5 mark on a lead line is a white rag. In maritime practice, lead lines are used to measure the depth of water beneath a vessel, and they are marked with specific intervals to help measure depth accurately. The 5 mark is represented by a white rag, which is tied to the lead line at that specific depth. This color coding is widely recognized in nautical navigation, making it easier for crew members to quickly identify the depth associated with the readings.

The use of a white rag is standardized to ensure uniformity across different vessels and crews, promoting effective communication about water depth and safe navigation.