I would eat the puke. Hopefully there is some nutritional content in there, and since I'm up to my neck in shit, that would be my best bet to stay alive.
I don't know about you Titus, but if I was up to my neck in shit, the last thing on my mind would be how I need some nutrition, and that eating some barf that's flying at my face could give me that.
I think I'd be more like "WTF IS GOING ON HERE MATE." Picture time!
I think the answer here is to not duck, because most likely, when you come back up from ducking, you'd get the puke on you anyway. Turn head if possible, but if not, just take it in the face.