title: Find land mass nearest to a geo coordinate
body: <p>As part of a developer challenge, I am trying to determine the land mass closest to a given coordinate.  Obviously, if the point is on land, I use reverse geocoding and can get details.  The problem is that if the point is in a body of water, especially oceans, it often won't return anything (Google, Nokia, Bing).  I'd like to know that a point 3 miles off the coast of California is 3 miles from USA, or x miles from Japan, y miles from South Korea when a point is reasonably near more than one country.  Is there any service that provides this information?</p>