Achievement is done on Chapter 4: Drylands Area 2: Tide of Battle
In order to get this achievement to pop, you need to be on the area , 'Tides of Battle'. A little ways pass the upgrade shop, you will see a Ship and Max will say something like, The Empire has drained the Sea. By then you should see sea mines in the dirt from the drained see. Shoot them so you wont get any damage from them and clear the whole area with out taking any damage from the sea mines and the achievenment should pop. If it dont, you should restart the chapter and try again, but remember, the mines are planted in the ground already visiable, so any kind of mines dropped from the enemie and causes you damage does not count so you can take damage from those, just not the ones already planted in the sand/dirt of the drained sea. Achievement will pop after completing the last little area of Tides of Battle.