Why do Mexican people put bags of water over their door?
All of them are right. When we go to visit my family in Mexico, we tie a bag of water over the table since it is an open air kitchen and it keeps the flies away. It does work. You sometimes will see some of the people in the open air market tieing them up above their fruit, meat, or seafood stands as well. It works well also for bees. I have lots of flowering plants all around my front porch and to keep the bees away from the front porch I have some beautiful hanging water globes around to deter them from coming up near the seating area. They are clear because colors do not work. Colors attract, clear scares them. Nothing superstitious about it.