Alright, so this is probably the trickiest of the 'find locations' achievements. If you would like screenshots of each location in these areas, here are the following as provided by
http://steamcommunity.com/sharedfiles/filedetails/?id=330160...Serenity Waste:
http://images.akamai.steamusercontent.com/ugc/52115787951227...Triton Flats North:
http://images.akamai.steamusercontent.com/ugc/52115787948113...Triton Flats Center:
http://images.akamai.steamusercontent.com/ugc/52115787946341...Triton Flats South:
http://images.akamai.steamusercontent.com/ugc/52115787948115...Stanton's Liver North:
http://images.akamai.steamusercontent.com/ugc/52115787949556...Stanton's Liver South:
http://images.akamai.steamusercontent.com/ugc/52115787949561...If you would just like to skip to the locations that you likely missed, check out Pyroclast Grotto in Serenity Waste, and Piraud's Trutch in Stanton's Liver South. Here are videos detailing how to discover each one:
Pyroclast Grotto (credit to Rooster Teeth):
Piraud's Trutch (credit to GameSpot):
If you have discovered both of those locations, just make your way through the locations in the Triton Flats screenshots and you will likely find one that you have missed. The last location I needed to find was Chandler's Hole in Triton Flats South. Happy hunting!