After gin is distilled, it must be mixed with water to bring it to a drinkable proof. That water should be as pure as possible, so as not to interfere with the flavor of the spirit’s botanicals. Martin Miller ships their distillate from England to Iceland, where rain and glacial waters collect 30 meters deep, within volcanic aquifers. This clean water goes straight from the ground to the bottle, its surface tension unbroken by purification processes like reverse osmosis. When the distillate is mixed in, this surface tension holds the alcoholic bouquet and burn in check, resulting in a mellow gin.