The water had filled the footwell of the deck and was creeping up the sides. About three quarters of the boat was underwater, the whole thing swaying with the roll of each wave.

‘She’s going down fast,’ Ellie said. She hugged Ben and turned to shore. ‘Ready?’

Ben took a breath. ‘As I’ll ever be.’

Ellie looked at him. ‘Stay together in the water. Look out for each other. No matter what.’

Ben nodded. ‘Of course.’

They climbed on to the stern, only a few inches clear of water now, looked at each other one last time, and dived in.

The shock of that first cold stab to her heart when she went in the water never reduced. The breath hammered out Ellie’s lungs as she stroked, feeling the chill in her bones. She kicked to the surface. Ben was just ahead, turning back to check on her. She waved briefly, pointed to shore, then began swimming, even strokes in the water, pushing the body of it behind her with every touch, every kick of her feet, every swish of her rubber-clad legs. Already she was warming up with the effort, her breath short but regular, heart thudding, the pulse in her ears mingling with the slosh of the water, the splash of waves, the wind whistling overhead. She was in Ben’s wake now, feeling the ripples from his body, the slipstream connecting the two of them like an invisible thread.

She heard a noise and turned back. The Porpoise had slumped on its side, taking on more water with a thwack and slurp, the port side of the hull exposed, but only a little, most of it already underwater. This could work, she thought.

She pushed towards land, imagining herself a porpoise gliding through the water as if it wasn’t there, at one with the sea. The water was her plaything, hers to manipulate. Her arms and legs were aching, but it was a good ache, it felt righteous and worthwhile.

Up ahead Ben was splashing through the waves. As the shore got nearer she could make out individual deer, their heads turned away, not worrying about anything approaching from the water.

She closed her eyes and breathed, head in, head out, breathe, just keep going. She pictured Jack sinking to the bottom of the Forth, weighed down by rocks. She pictured Logan falling through the air, less than six elephants to destruction. She imagined Sam doing the same, meeting up with his father and Logan at the bottom of the ocean, a crowded bustle of all the people who ever died in the Firth of Forth, all suddenly alive and sharing their stories, the terrible, ordinary lives that had led to their deaths, a thousand people jumping off the bridge since it was built, more than the congregation of a church, or the entire roll of a school, all waiting on the seabed for others to join them, for Ben and Ellie to join that blissful release.

Ben was slowing down ahead of her and she caught him up. They were still a hundred yards from shore. He said something to her but she couldn’t make it out, then his head went under. She stopped, treaded water. His head and one arm came back above the surface, his other hand reaching down to his lower leg, grabbing at his calf muscle.

Cramp.

His head went under again.

She waited a few seconds.

This time he didn’t come back up.

She dived under, trying to see through the murk, the saline stinging her eyes. She powered over to where he had disappeared, grasping at the water, pushing downwards, turning and stretching her hands out. She saw movement out the corner of her eye and spun round again, kicked and stroked towards the swirl in the gloom. She spread her arms and made wide sweeping movements from left to right. Eventually she felt the material of his suit brush against the back of her outstretched hand and grabbed at his body. She got a hand under his armpit and hauled him upwards, kicking furiously to get back to the surface. She could feel his heartbeat through the wetsuit.

They broke the surface, Ellie gasping, Ben coughing and choking.

‘I’ve got you,’ she said.

She leaned back and pulled him with her arm around his chest, her other arm making deep strokes in the water, her legs kicking hard under his body. Ben was limp in her embrace to begin with, then slowly began to stroke with his right arm, the one he had free of her body. Between them they started to get some momentum, small surges through the wash, every stroke taking them a few inches closer to land.

‘Sorry,’ Ben spluttered through the water.

Ellie shook her head and whispered in his ear. ‘Don’t speak.’

She shot a glance behind her. The shore was seventy yards away. She felt the muscles in her thighs and calves begin to cramp up, burning spasms. She rested a moment then kicked again, the pain returning stronger, her arms thrashing in the water, the waves bobbing over their mouths as they slipped under then came back up for breath, salt on her lips. More strokes, more kicks, the last of her energy draining, Ben’s too, she could feel it, just keep going, keep stroking and kicking and breathing. Stroke, stroke, stroke. Gasp for air. Her lungs heaving, legs on fire, arms like jelly, Ben’s back on her chest, the two of them a single entity fighting to stay alive.

She snuck a glance behind. Forty yards. They were moving excruciatingly slowly now, hardly making headway, their heads dropping below the surface, then back up, necks strained to gulp in air. All Ellie could hear was her heartbeat in her ears, roaring. She kicked and kicked but her muscles refused to respond, constant cramp and spasm, no energy left. They ducked under the water again and Ellie thrashed her arm and legs, trying to get back to the surface. Ben was a dead weight on top of her now, pushing down on her chest. Her lungs ached and she longed to breathe, the urge to open her mouth almost overpowering. She kicked through the pain, through the cramp, sweeping her hand out, moving upwards inch by inch, so close to the surface she could almost smell the salty air, her muscles seizing up all along her legs from her groin to her toes.

She broke the surface, heaved in air, thrashed her limbs, panic filling her mind, kicking and pushing through pain like she’d never experienced before, Ben still in her grasp, his head lolling backwards.

They went under again, Ellie gulping in a mix of air and water as they sank. Her body was empty, utterly drained, as she stroked weakly and tried to muster her legs to move.

She kicked out for what felt like the last time she could manage, and felt pebbles scrabble and tumble under her toes. She threw her leg out again, scuffed her heel against the bottom, tried to get purchase, kicking towards shore, kicking to get her footing. She lost balance and sank down again, Ben’s body pressing on her, then she began to get a solid footing on the stones, eventually managing to dig her heels in until she was suddenly standing, her feet on the ground, her body connected with the solid earth, as she hauled Ben with her.

‘Ben,’ she said. ‘We’ve done it.’

He didn’t speak, didn’t open his eyes.

She felt ground under her feet as she walked backwards. The cramp surged through her calves and thighs. She grabbed Ben by the scruff of his wetsuit and dragged him towards the beach, staggering and stumbling as her legs gave way, her arms numb.

She got him to the edge of the beach and collapsed next to him.

‘Ben.’

Nothing.

She rolled him on to his side, hit his back hard.

Nothing.

‘Fuck’s sake.’

She put him on his back, pinched his nose, tilted his head and placed her mouth on his. She’d seen in an advert somewhere that you didn’t do that any more, but fuck it, that’s the way she’d been taught.

Stopped and pushed on his chest six times. Six elephants.

Went back to his mouth, did the same again.

Then the chest.

Nothing.

She slapped his face hard. ‘Come on, Ben.’

She pinched his nose again, breathed into his mouth, taking large gulps of air in between and blowing till her cheeks burned.