arcgis desktop - Extracting coastline as vector from landsat 8 imagery?

I am trying to detect some sea level rise/fall for a specific region, from Landsat imagery.

I went through the recommended methods of identifying water/land (MNDWI, AWEI, Bandratio 5/2, etc.).

Now I am at the point where I need an accurate vectorized coastline. I tried with Geomatica Lineament extractor, but somehow I wasn't happy with the results.I have Geomatica 2013, ENVI 5.3 and ArcGIS 10.2.

Answer

I was going to suggest you convert the classification map to a vector map which then can be used to identify the coastline. But then I realized that what you are trying to do eventually is change detection. If you are indeed interest in identifying the area of change between multiple images, you can do that without extracting the coastline. Just overlay the classification maps and using Band Math in ENVI, you can assign different values to different change types (ie, unchanged, increased, decreased, etc).