You don't breathe on your own anymore. Hold a key to inhale, hold another to exhale, keep the cycle going or you suffocate, even on dry land.
Vanilla lets you forget your lungs exist. Inhale doesn't.
Your air meter no longer refills by itself. Breathing becomes a two-step cycle you have to keep alive every few seconds, and it runs on dry land, not just underwater.
Breathing has two phases, each bound to a key you hold:
Inhale with "V" to fill the air bar one bubble at a time. Stop inhaling and the air leaks away.
Exhale "B" once your lungs are full you must empty the bar, one bubble at a time .