Sometimes, the hero is trapped in a room that begins suddenly to fill with water. For whatever reason - maybe a burst water pipe or smashed aquarium or malfunctioning sprinkler system or even, perhaps, because the room itself is underwater to begin with, like the control room of a submarine - a torrent of water rushes in.
The hero tries at first to escape. She kicks at the door and then, finding it won't budge, tries to pull the grate out of the ventilation shaft. She swims across the room, looking for tools - a letter opener, a crowbar - and although she sometimes finds these things, they are useless.
The room becomes separated into two layers, like a salad dressing. The bottom half, obviously, is water, above which the remaining air floats like oil. The submerged portion of the room is transformed. Papers, previously stacked neatly on the corner of the desk, become snarls of watercress.
The surface of the water - too turbulent to have formed a meniscus - is the dividing line between two worlds. Below, it is strangely calm. Above, there is foam and noise. If there are others in the room besides the hero, this thin slice of air, narrowing by the minute, is where they will shout, hatch plans and comfort each other. The hero ducks into the water again and again - swims with blocked ears through the slow-dancing shipwreck looking for a forgotten window pane or laundry chute - but returns always to the surface to breathe.
In time, the hero will run out of options and tread water with her forehead touching the light fitting. The others will tire and disappear one by one. As the level rises further, the hero will tilt her head back until at last only her nose and lips remain above the surface, pressed to the plaster, taking rapid little sips of air.
It's okay, though, because the hero knows that something always happens at the last minute. She will prevail. She will be rescued. The flow will abate to a trickle; a wall will give way. There will be a miracle.
The hero, in fact, is wrong. There's no plot twist. The water always fills the room completely. The room never contains an exit. The hero never escapes. But that space at the top - that twenty, fifteen, ten, five centimetres of air between the ceiling and the encroaching surface of the water - that space is enough. Until it isn't.
[This story also appears in HEAT 7]