I know this isn't about a mouth full of dirty tank water, even though it's happened to me a bunch of times. It usually happens when you suck on one end and it isn't enough to draw the water out, so you take a big suck and get a mouth full of dirty water. However, the worst thing that has happened to me was getting a mouth full of gas. I was donating our mini-van because it just cost too much to fix but I had filled it up with a full tank of gas. I decided, since gas is so expensive now, that I would siphon the gas out into a can. Well, at least you can see the water going thru the hose but you can't when you siphon a gas tank. I swallowed a mouth full of gas and I felt high for the rest of the day. Really nasty, The Doctor