What is MARK 25 on the lead line marked with?

The MARK 25 on the lead line is designated by tying one knot in the line. This specific knot serves as a reference point to indicate a depth of 25 fathoms, which is critical for navigational purposes. The purpose of marking the lead line is to allow for quick and precise readings of water depth, ensuring safe navigation and operations while at sea.

Each marking on a lead line corresponds to a specific depth measurement, and the use of knots helps crew members easily recognize these measurements without having to count individual markings.