Just another slightly off topic note - waterborne disease is a huge issue in undeveloped countries. I used to do volunteer work with a missionary organization and clean water is an enormous issue affecting infant mortality rates. With that said, here's a tip that can work with unclean water - The missionary organization advised those going oversees to begin eating plain yogurt twice a day for 2 - 3 weeks before traveling to the middle east, central asia, and northern africa, and south america. The good bacteria in the yogurt helps kill a lot of bad bacteria and helps stave off montezuma's revenge and the sudanese shuffle.