Beach: The beach is an accumulation of Unconsolidated sediment(sand,shingle,cobbles, etc,.) extending from the mean low tide line to some physio-graphic change such as a sea cliff or dune field or to point where permanent vegetation is established.
Instead of coast ans shore we use generally coastline and shoreline.
Shore: That strip of ground bordering any body of water which is alternately exposed, or covered by tides and/or waves. A shore of unconsolidated material is usually called a beach. The demarcation line between water and land is called shoreline.