Keep trying.

The maid laughed cruelly at Rita's squirming displeasure. She blew a kiss and strode away, out of Rita's field of vision. Refusing to give up, Rita continued to examine the interior of her prison. She swam in circles, round and round the edges of the tank, looking for something, anything that would help her escape. She became steadily more depressed with each circle, it didn't take her particularly long each time.

After about 10 circuits, she collapsed onto the glass floor, a wave of tiredness overtaking her anger. The tube **** her to breathe at a steady rate and she couldn't manage long efforts without getting out of breath. The tube was more powerful than her own lungs but her instincts overtook her as her chest started to ache. As the tube breathed her lungs out for her, Rita tried to breathe in again, sharply. Immediately, the tube shut down, it seemed to be blocked. She strained desperately to breathe, her chest ached, her lungs burned but the tube remained closed.