How to draw coastline shp file on GeoServer?

I've downloaded the coastline shapefile and loaded it into my PostgreSQL/PostGIS database, then added the osm_coastline.sld style into my GeoServer. I am able to draw the coastline in combination with a Natural Earth II image pyramid. However, the coastline file seems to be made of many small squares, some of which actually have edges that are coastlines. Is there some way to specify the style such that the interior lines are not drawn but the actual land/water interfaces are?

Thanks! Thom