strandline

noun

1. The linear mark left (on a beach etc.) by high water; (geology) the line that marks the interface between land and water; a shoreline; it changes daily, and over geologic time.

   “The beach strandline is just as much a wildlife habitat as a woodland or wildflower meadow, and every bit as diverse and interesting. It has a dynamic nature, changing every day as organic debris from the sea is deposited on the beach to be gradually broken down by the strandline inhabitants; sometimes the whole strandline is buried in sand or shingle or submerged by storm waves.”