Thick droplets of water rained down from the ice sheet, dropping out of a dense fog. The river bed twisted up ahead to the right. Beyond that, we’d probably never know.

What if there was water around that bend?

My eyes returned to the gauge monitoring the exterior pressure. How much could the human body handle? The ice sheet was obviously off the scale, but 228 psi— that equated to free diving in about 350 feet of water. The world record for free diving was about 420 feet. I was certainly no diver, but leaving the sub wasn’t about holding my breath, it was about being able to handle the extreme pressures that would be squeezing my ears, sinus cavity, and lungs—something I had faced years earlier when our submersible had suddenly cracked open in the depths of the Sargasso Sea.

If water was out there, could we drag the sub to it before our air cavities ruptured?

I was about to broach the subject with my bickering shipmates when we felt the river bed beneath us rumble.

Silence took the sub. I quickly shut down the Valkyries while Ben extinguished our exterior lights. Huddling in the dark, the three of us searched the landscape using our night-vision goggles.

The reverberations were getting closer, and then a creature appeared over the rise and I forgot all about venturing outside.

It was a Purussaurus, a pregnant female, I surmised from its labored gait. Staking out a sand-covered expanse close to the river bed and less than fifty yards from our sub, the eighteen-ton prehistoric crocodile began digging a hole with her clawed hind feet while her enormous tail swished back and forth, flicking debris in every direction.

Ben backed away from the glass. “Mother of God… I seriously need to be drunk.”

Sand rained across the pod, obscuring our view. I heard Ben offer Ming something. A moment later, he leaned over into my cockpit and passed me an open whiskey bottle. “A gift from your Viking pal. Go on, it’ll make it easier.”

I took a long swig and passed it back to him. “I feel like such an arse. For the first time in my life, I had it all—the girl of my dreams, a son, a prestigious job. Why’d I do it?”

“You’re a scientist; you did it for the work.”

“No, it was my stupid ego. Over three thousand people have climbed Mount Everest, hundreds have been in space, but Vostok—I wanted to be the first, the Neil Armstrong of subglacial lakes, the marine biologist who ventured back in time.”

“I suppose that makes me Buzz Aldrin. Want to know why I took this mission?”

I glanced at the air gauge. “You have fifty-seven minutes, go for it.”