Summer tried to move, squeezing her eyes shut as she pulled at her leg, but it was no use. “My foot is pinned,” she said. “Tight.”

Dirk crawled over for a better look. The collision had driven forward one of the oxygen tanks, which in turn had mashed the lower floorboard. A plate of reinforced steel had curled up, catching Summer’s ankle against the seat’s housing.

Water had already risen past her calf when Dirk reached down to examine the buckled plate. “Can you pull forward?”

She tried, and shook her head. “No good.”

He maneuvered past her. “I’ll try to move the housing.”

With his back braced against the acrylic bubble, he placed his feet against the housing and pressed with his legs. Because of the awkward angle, he could apply only a fraction of his full strength. The housing rocked slightly, but nowhere near enough to free Summer’s leg. Dirk tried a few other angles, attempting to rock the housing, but without success.

“I just can’t get enough leverage,” he said.

“It’s okay.” Summer spoke calmly, trying to mask her own fear and not place undue pressure on her brother. “Water’s rising. Better get the dive tanks.”

Dirk saw the water was already up to Summer’s waist. The leaks had increased, and the cabin was filling quicker. He dropped his legs into the water, which stabbed his skin with an icy bite, and climbed past the seats to the rear of the submersible. He reached for a rack next to the hatch that held emergency evacuation gear—two dive tanks fitted with regulators and masks.

He passed one tank down to Summer and looped the other over his shoulder. Then he rummaged around a compact toolbox, cursing that its wrenches and pliers were designed for small electrical repairs. The largest tool was a ball-peen hammer, which he grabbed, along with a short hacksaw blade. The blade summoned up the image of Aron Ralston, the courageous mountain biker who cut off his own arm after becoming trapped under a boulder near Moab. Amputating Summer’s foot with the hacksaw blade might become a gruesome last measure to save her life.

“Any ideas?” Summer asked when he climbed over with the tools.

“I’ll try and wedge the seat frame apart so you can slip out.” He passed her the light and hoped she didn’t notice the saw blade.

“Okay,” she replied, shivering as the cold water swirled around her chest.