system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we gasp for air when we shower with cold water or we enter in a cold pool?

Title self-explanatory, please explain in simple terms.
gpt
The rest of your body, and sometimes even parts of your brain don't always have access to the most accurate information about what's happening to you. *You* know that you're just stepping into the shower, but the circuits of neurons deep in your brain and spine looking out for your survival don't really care about that. 

Our distant ancestors had to deal with falling into a freezing lake long before they evolved self awareness and rationality, so your reflexes don't really know the difference between a cold shower and falling into a freezing lake. Your reflexes know that this *feels* like a life threatening situation, so the natural response is to prepare for action. That gasp, along with the tightening of your muscles and a spike in your heart rate is a reflex that we used to need all the time back when we lived in the wild. Now we live in an environment that's way safer than what we evolved in, but our reflexes are still built for the wild.