Yes. If you want to draw a straight (not sure if you mean as in straight line) coastline, all you need to do is the following:
If for an island use the SMOOTH POLY tool.
If it is for a coastline that goes 'off' the map then use the SMOOTH PATH tool, and then attach some straight lines to the coastline where it meets the map border, tracing around the outside where the border would be. Using the MULTIPOLY tool makes that into a solid poly you can then use the CHANGE PROPERTIES tool to change the color/fill style etc of the land.