After a 10-minute swim, we suddenly came to a maze of underwater canyons thick with enormous sponges and coral fans, around which schools of circus-colored fish zigzagged. Plump purple sea pens with feathery quills stood in sand inkwells. Tiny tube worms — shaped like Christmas trees, feather dusters, maypole streamers, parasols — jutted out of the coral heads. Sea relationships are sometimes like those in a Russian novel; a worm enters the larder of a fine, respectable coral to steal its food, and just stays there, never being evicted. I moved my palm over a red-and-white striped parasol, and in a flash it folded up its umbrella and dragged it back inside the coral. It’s a game divers love to play with tube worms: abracadabra, and the tube worm vanishes.

On a coral butte just in front of us, a dark sea whip jutted out between the canyon walls, its Medusa-like hair straggling in the current. I laughed. That sea whip’s hair is just like my own.

Then I remembered: We’re mainly salt water, we carry the ocean inside us. The simple, stupefying truth that, as a woman, I am a minute ocean, in the dark tropic of whose womb eggs lay coded as roe, floating in the sea that wet-nursed us all, moved me deeply. I pulled my mask up and washed my face with salt water, fitted it back on and exhaled through my nose to clear it.

From then on, I was hooked, and often returned to the sea to re-experience the visible links of that invisible chain.