Remember her essay at the beginning of the movie:
"I carefully enter this wild and beautiful, unexplored underwater world. I swim in silence...only my breath disturbs this stillness. There is nothing above me but the shimmering light. The place from which I came, and to which I will return when I am finished here........
...I check my oxygen; I don't have much time to see everything I wanted to, but I'm glad I was here."
It's almost as if she's writing about this movie and not about diving...