My son (age 13) came home from a short camping/hiking/climbing trip of three days on Saturday. They were gone Thursday-Saturday. They took drinking water, but swam in a local creek/river?. He told me he swallowed some water while swimming. Not a lot, but a good mouthful. Today he is VERY bloated and has started having very greasy, floating, foul smelling diarrhea. He says he doesn't feel too bad, just crampy and not hungry. I immediately thought giardia, but all the info I have found says that it is too soon for that. Anyone had it before and how soon after exposure did it show up? Edited to add: I will definitely take him in to the doctor if he still has this going on in a couple of days. Not looking for medical advice, just curious.