How did Jennifer Lawrence's character survive SPOILER ALERT

How did she survive her near-drowning?

She's swimming in the pool when the gravity shuts down and she gets trapped in a huge floating globe of water. She passes out and convulses and seemingly that's it for her. Then the gravity comes on again and she falls with all the water back into the pool, never reaching air. 30 seconds after she passes out, she somehow regains consciousness while under water and bursts to the surface, safe and sound.

The least they could have done to make this realistic is to have her land on the outside of the pool when the gravity came back on and have the force of impact propel the water from her lungs.

I've never heard of someone passing out due to drowning and then waking up 30 seconds later still submerged, with their lungs still full of water.