Shark Week:
The week during which a woman has her period. There will be blood, an uncomfortable sense of tension and a bad tempered, unpredictable beast.

Take heed during shark week. If you show signs of weakness or aggression, you will be attacked. If you get attacked, it will be all your fault, infinitely more traumatic for her and you'll never be allowed to forget it.
Man 1-"Why is your wife glaring at you from the window?"
Man 2-"Shark week. She's looking for an excuse to strike"