Bottled water does not conduct electricity.
Based on the name, Luke was able to discern that the bodies were positioned to point True North instead of magnetic north. Although magnetic north is about 500 kilometres away, (it is somewhat fluid because of the changes in lava mass under the earth's surface, which is what causes the magnetic pull) it is located in Ellesmere Island which is part of the Qikiqtaaluk Region in the Canadian territory of Nunavut, lying within the Canadian Arctic Archipelago which is considered part of the Queen Elizabeth Islands. Canada is directly north of the United States. A line going from Arizona to True North would run directly across Ellesmere Island making the line virtually the same and at least the difference would be imperceptible if it were not a key plot point.