I'm just wondering, if you sneeze under water will you drown?

Not likely: Sneezing is an involuntary reflex to something that irritates certain areas in the nose . It is sudden inhalation followed by the forceful exhalation that we call a "sneeze". This could get tricky underwater, but people have experienced this and lived to tell about it. Basically most people feel it coming on and resist the inhale by keeping mouth closed; that's the trick to not drowning ;).