I have downloaded ETM and TM images from Earth explorer, and trying to extract shoreline from the iimages which is bit confusing. I want to demarcate high water line or shoreline from the images.
Check the Landsat Toolbox for Shoreline Extraction tool. This tool was built for ArcMap 10.0. Check if it works with your version of ArcMap.
Also see the following PDF for the steps.
Using ArcMap to Extract Shorelines from Landsat TM and ETM+ Data
Retrieving data ...