I have NGA shoreline polyline shapefile of Indoneisa. I have modified it by adding two lines to close the polygons, so that I can create a polygon of my area of interest. However, there are numerous waterbodies which are drawn in the shapefile, and when I am trying to create a polygon from the polyline, a closed polygon is not being created. I tried dissolving the polylines but that didn't help either. Any ideas on how to do it? Otherwise, I will have to manually delete the polylines which are interrupting in the creation of the polygon.
I am attaching a portion of shapefile I am working with (the complete one is too big to be attached here). Any help will be greatly appreciated.