Coastline data sets
In OpenStreetMap the primary division of the earth surface into land and water is mapped through ways tagged with natural=coastline. For rendering a map however you usually need land or water polygons representing continents and islands in the former or oceans in the latter case.
Assembling these polygons from the coastline ways in OpenStreetMap is done with a specialized processing tool (OSMCoastline). Learn more about the coastline processing...
The results of this can be downloaded here.
Polygons for all land areas in the world, ie. continents and islands.
Polygons for oceans and seas.
Linestrings for coastlines.