I can't quite tell what the best conditions would be.
All air in your lungs would immediately be forced out. That would probably happen through your mouth, but it's possible that your chest would pop like a balloon. You would have a sudden and critical case of
the bends, causing sharp pains in every joint and probably stopping you from moving in any way. And every fluid in your body would boil and evaporate away.
Sooo... I'm going to say about half a second.