She's scared and wet.

Mallory knows that she can't get out.
She knows that she has to trust her boyfriend.

Kind of hard to in this situation though, no?

She seeks the last vestiges of air...

She'd later learn that she was being filmed for all of this.

Her man got a great shot of her looking for an escape through the see-through top plate.

It is a reminder of who's in charge.

The box fills up.
She panics.

The man watches her.
He's going to enjoy this one moment before he has to stop it.

He waits a moment.

He then sets the box to drain and then presses a button.
The top opens and he quickly presses her head through it to get air.

She was never in danger.
He'd never tell her that.

"So...do you want to get out of that box?"
Mallory nods.
He smiles.
He has plans for her.