How long does it need to take?
 

By some strange quirk of circumstances just you and a doctor are stranded on a desert island together. There are various sources of water on the island, but you don't know which, if any of them, are safe to drink from? Do you:

A. Do nothing until the doctor prescribes something, and wait for him or her to search for something that can be patented, before organizing and then running a double-blind, placebo controlled clinical trial with preliminary results due in five years time, which may get regulatory approval a year later and which may come to market at a price you can afford?

B. Start by one of you drinking a small amount from the cleanest looking water source?

John

Ha!
 

It's gotta be option "b"....and the doctor says "you first":)