When the instructor tells you not to do your first dive hungover, just obey.  No matter how much fun that party you're at is, or how hot the girl you're talking to appears to be, or how much peer pressure your buddy with the hands full of tequila shots is putting on you.  Just don't do it.  The amount of fun you have the night before is an inverse correlation to the amount of asphyxiation-induced-terror you're about to have the next morning when you vomit into your regulator 50' below deck. Yeah, I think that about covers this one.

Still gets two stars because I was nudged by a seal.

In hindsight, he was probably just following the puke trail.