We (and many other mammals) have what is known as the mammalian diving reflex. It’s a hard-wired psychological response to immersion in cold water. When trigger

We (and many other mammals) have what is known as the mammalian diving reflex. It’s a hard-wired psychological response to immersion in cold water. When triggered, our heart rate slows, blood is redirected towards our core to protect critical organs, and a host of other energy and oxygen conserving mechanisms come into play in anticipation of us holding our breath for an extended period underwater.