I would go Megaton, save the place from the big scary bomb then just drink the water given to me by my super cool robot assistant at my new and cool house. Or, I would sneak about stealing everyone else's water and have it all for myself. Lol.
I would try to keep calm and think about my life . If I could, I would walk around till I meat my death if this happened because we are all going to die anyway even in natural death.