Everything changes around Isabel Sánchez-Arán when she descends to the bottom of the sea. The lights, the temperature, and the pressure. "When you go down, you're always afraid; it's a mechanism we have to stay alive," she explains. But she can't stop herself from going deeper and deeper using only the strength of her lungs, without an oxygen bubble. These days, Isabel will try to be one of the first women to break the 100-meter barrier in apnea. That is, 100 meters while holding her breath.