http://www.nefkom.net/z-bau/celestia/
Don't be confused by the doubles and triples of identical names. Ocean or Seafloor specialists don't seem to be very imaginative.
Technical:
I decided to set all types in this file to 'ME' -> maria(sea), so be shure you checked this option in your Celestia locations menu. I couldn't see a better solution, althought this classification is reserved for moon mares.
An alternative was to be more specifical and classify mountains, hills, valleys, highland, lowlands, ... , as the USGS classification allows, but this would of course interfere with land structures. I would like to see some comments of how you think this could/should be handled.
maxim