It does assuming you are using a snorkel that is in the front in line with your nose (not the scuba kind of snorkels that are on the side).
When you flip turn and are on your back, the snorkel should be in between your arms while streamlining (you'll need to have a good streamline). It will move a bit as you push off and turn but your arms should keep it from getting completely screwed up. Do not break streamline until you have fully rotated onto your stomach.
I sometimes will need to adjust it mid pool and I can do that just by nudging the snorkel with my bicep during the recovery phase of the stroke.
edit: it should be obvious that you will need to clear the snorkel as you surface after each flip turn.
blog