Have you ever noticed that when you swim underwater, you can hold your breath for much longer than if you were just sitting above water not breathing?
This is because of a physiological response known as the mammalian diving reflex. When cold water (lower than 21 degrees Celsius) touches your face, changes happen in your body that allow you to hold your breath for longer. Let me just break from my professional tone for a moment:
THAT IS SO COOL!!!!
The human body never ceases to amaze me.
(Warning - jargony biology-talk ahead)
I particularly like this because it supports the idea that humans retain features that are adaptations to an aquatic lifestyle, whether from the primordial soup that all life on earth evolved from, or whether humans as we know them - bipedal apes - once lived in a soggy environment that selected for features such as our down-turned nostrils and the webbed fingers and toes that some people still retain (I have heard of people being born with non-functional gills below the skin of their necks too, but this is probably related to the primordial-soup origins). Some biologists argue this aquatic origin theory passionately, saying that our long, muscular legs first evolved for swimming, and became useful for running later, after our wet habitat dried out, an idea I quite like on the basis of whimsy but one that I have not yet committed to in terms of scientific belief.