I used 1" dacron webbing marked in feet with a permanent marker
and sewn on by hand every 30' on my 330 ' of chain (30', 60', 90', 120', etc). That way each mark gave me a 5:1 scope to the depth in fathoms, or if i lost count, I could just read the mark. On the same link as the first mark you can add one cable tie, and add an additional tie on each subsequent mark so you can count the marks in the dark (or in the daytime if the mark comes up covered in mud). The reason I don't use paint is; I intend to end for end the chain, when one end begins to lose its galvanize.