Legal Definitions - high-water mark

A high-water mark is a mark that indicates the highest point to which water rises or falls. This can refer to:

1. The shoreline of a sea reached by the water at high tide. This is usually calculated as the mean or average high tide and not the extreme height of the water.
2. The highest point on the shore of a freshwater lake created by a dam in an unnavigable stream to which the dam can raise the water in ordinary circumstances.
3. The line that a river impresses on the soil by covering it long enough to deprive it of agricultural value. This is also known as the high-water line.

For example, if you go to the beach and see a line of seaweed or debris on the sand, that is likely the high-water mark from the previous high tide.

Low-water mark, on the other hand, refers to the shoreline of a sea marking the edge of the water at the lowest point of the ordinary ebb tide or the point to which the water recedes at its lowest stage in a river.

Overall, high-water mark is a term used to describe the highest point that water reaches in a particular body of water, whether it's a sea, lake, or river.