The line that marks the separation of land and water along the margin of a pond, lake, sea, or ocean; also called the shoreline. The strand line is very dynamic. It changes with the tides, storms, and seasons, and as long-term sea-level changes take place. The sediments on the beach respond to these changes, as do the organisms that live in this dynamic environment. On a beach organisms move with the tides, and on a rocky coast they tend to be organized relative to the strand line because of special limitations or adaptations to exposure.