Supplement 1, The South China Sea is the first intended supplement for Mariner.  It is the published setting for the game and assumes the same position with regard to Mariner that The Spinward Marches did for Traveller.  It will detail specific ports, trade routes, points of interest, and hazards found in and around the South China Sea.

In actual publication, I would like to see Supplement 1 included with the three basic rules books.  Possible future setting supplements might detail other maritime hotspots such as the Indian Ocean and the Mediterranean.

Here is a link to a good map of the South China Sea.