Normally just get the lung capacity meter above 50-60 (you dont need to have your lung capacity at 0% to inhale again, just dont inhale right after you start exhaling or else you lose oxygen) )
then exhale. remember to keep your oxygen above 70% unless you're running/jumping or doing some sick parkour

for speeds faster than walking: since your breathing is sanic speed inhale for a short second and then exhale (dont worry if you go under 70% O2)) and repeat. After you've stopped being a fast boi take your lung capacity to 0 and then take a deep breath, this will take you to 100% oxygen.
Don't inhale water and stay ascended 🗿