The order to vacate comes when the building starts to slowly fill with water. Hallways begin to swell— a kind of edema. But unlike a patient near the end of life, a building can't be set on its side; can't be propped up by pillows so gravity might help re-distribute the surplus of fluid. We know it doesn't take a lot of water to cause drowning. One can drown in four inches of bathwater after inhaling even a quarter cup of water. A fish out of water spasms and suffocates. There's something called dry drowning, in which water never even reaches the lungs. Not everything that moves in water can breathe under the surface; even the professional mermaid can only last five minutes before she has to haul her glittering monofin out of the pool.