My friend is right

...we are all sea creatures. We can up from it, and our bodies are mostly water. I don't know the details, but our blood's saltiness is very similar to that of sea water.

I grew up on the ocean. My second childhood home was right on the beach. Some mornings the family would get up really early and go swimming. I remember as an older child going swimming during storms -- yes, young and dumb -- yet it was thrilling and delighful; the pattern of the waves was choppier than usual, and body-surfing was a different challenge. And it was water everywhere: water coming down, water underneath: a feeling of opening wings, and flying.