He smiled in the darkness. ‘You know this stuff better than me. Okay! Let’s fire her up – and hope the propeller isn’t still embedded in the cave’s ceiling.’

Even with the life vest, Nina felt as if she was sinking. The cold water was rapidly draining her energy, and her fingertips and toes prickled with the onset of hypothermal numbness. If she stayed in the water for much longer, she might not get out of it . . .

‘You’re almost there!’ Cheng had kept pace above, moving to the stern. ‘To the left, you’ve almost reached it!’

She still saw nothing but icy slush rising and falling in the waves – then caught a flash of yellow. Twenty feet away, no more. The sight gave her new vigour. She ploughed towards it. The pouch bobbed into view again. Ten feet, five—

And there. She grabbed it with one cold-stung hand and forced it beneath her harness strap, then turned to swim back to the crane.

Imka made a final check of the gauges – and pulled a lever.

The steel hoses shook as a powerful whump of compressed air surged through them. Machinery groaned, forced into motion . . . then the engine abruptly clattered to life as the diesel fuel in the cylinder auto-ignited. The contained detonation drove the piston back, turning the great steel crankshaft. The other cylinders followed suit, the room filling with a ragged roar as the engine built up to speed.

Eddie gripped the console as the deck lurched. ‘We’re moving!’ he cried. ‘Let’s get to the bridge – and hope we can steer this thing!’

A churning surge rushed up from beneath Nina. Froth rolled over her head. She surfaced, coughing and gasping—

And went under again.

Something was dragging her down. Even with the vest, she couldn’t keep her head above the water. A pounding metallic rumble assaulted her ears. The ship’s engine had started – and the propeller’s vortex was sucking her in as the Dionysius reversed towards the cave mouth.

She kicked in a desperate attempt to make headway. But the force was unrelenting – and then the reversing juggernaut’s stern rolled over her.

Nina clawed at the hull, fingers finding dents and barnacles, but nothing big enough to grip with her numbing hands. The propeller whirled below. The life vest strained uselessly to lift her, straps tugging painfully under her arms.

She slipped further down. The propeller was just feet away, slashing blades about to hack her apart—

Something writhed past her.

Rope, whipping like an angry snake as it was pulled towards the propeller. She grabbed it. For a moment both she and the line kept falling – then it yanked tight.

She clung to it. For agonising moments it remained still . . . before it inched back towards the surface.

Nina closed her eyes as she rose through the floating ice, then felt frigid air on her wet skin. The cold stung her throat as she took several deep breaths.