tidemark

A line or mark on a shore indicating the highest or lowest level reached by the tide.

A trace or indication of past activity.

The limit of the flow or of the ebb of the tide.

a mark on a shore line indicating the normal level of the water at high tide, caused by the action of the flowing water; sometimes also used for the mark left at the point of the normal low tide; — called also high water mark.

the maximum level which some activity has reached and from which it has declined; — called also high water mark.

a line (of seaweed or differently coloured sand etc) on the shore showing the level of high or low tide

any mark showing the limit of some past activity

a line of scum left on a bath tub when the water is drained away

indicator consisting of a line at the highwater or low-water limits of the tides