The Deepest Dig

Brooke Jarvis: On the nights before a dive, Cindy Lee Van Dover likes to stand on the deck of her research ship, looking down into the water the way an astronaut might look up at the stars.

She's preparing herself to do an extraordinary thing: climb into a tiny bubble of light and air and sink to the bottom of the ocean, leaving the sparkling waters of the surface a mile and a half above her.

She makes the trip in a three-person submersible called Alvin, famous for discovering the underwater hot springs known as hydrothermal vents and for exploring the wreckage of the Titanic. Alvin sinks for more than an hour. The view from its portholes moves through a spectrum of glowing greens and blues,…