Don't need to breathe

The ocean shook for a moment, then whipped up into a series of waves, rapidly receding away under Cell and revealing the muddy ocean bottom. The few remaining structures on the sunken island were immediately blasted into matchsticks as the crumbled ground shuddered under the rush of energy. The ocean floor didn't look anything like they expected, but that was probably because of all the recent changes. Still, seeing over a hundred feet of water held back by an invisible wall of energy was quite impressive.

"There she is!" shouted Gohan over the roar of the waves. Sure enough, 18's limp, unconscious body lay half-buried in the murky bottom. She clearly wasn't breathing, but apparently Gero's cybernetic modifications had rendered that unnecessary.

- Bringer of Death Chapter 52