Rosie was an excellent swimmer, but Paul’s stroke was weak and she held on to his life jacket and begged him to kick. The jackets made them buoyant, but the rapidly sinking ship created a vortex under the water that was dragging them down.

After half a minute of fighting to get away and as more desperate souls threw themselves into the water, the stern of the Cardiff Bay went under, leaving a great circular depression into which everyone and everything was sucked. The epicentre was less than ten metres from the Clarkes and the twisting water flipped one of the few lifeboats to have been successfully launched. A dozen passengers were trapped under the upturned hull as it was sucked down.

As a huge air bubble blew out of the depression, a powerful current gripped Rosie’s legs and pulled her deep underwater. She tried keeping hold of Paul, but it was pitch black and they broke apart when a wooden oar smashed her in the back. She reached in all directions, but he was gone.

The urge to breathe was becoming overpowering and Rosie was sure that she’d drown. While the cold water made her skin feel as if it was filled with needles, she knew she’d die if she didn’t surface quickly.

Then, as swiftly as the current had swept her under, the water around Rosie became still. No bubbles, no chunks of debris, and she felt the life jacket start to pull under her arms. The current rushed against her body as she came back to the surface and she put her ankles together and arms at her side to streamline her shape.

Her ears popped as she broke the surface and took the biggest breath of her life. But her relief was short-lived.

‘Paul,’ she screamed, as she gulped air and spun around, studying the debris and bobbing heads on the flat plane of water surrounding her. The nearest was a fit-looking fifteen year old with curls of black hair stuck to his face. He ploughed through the water towards Rosie and took it upon himself to rescue her.

‘Are you hurt?’ he asked, in French tinged by a slight American accent.

But Rosie was frantic for her brother. ‘Paul!’ she screamed. ‘Paul, where the hell are you?’

‘Calm down, save your breath,’ the American said firmly. ‘Did Paul have his life jacket on?’

‘Of course!’ Rosie said.

‘We all got sucked down. He could have surfaced a hundred metres from here. How about you? Are you OK?’

Rosie nodded as she kicked her legs gently under the water. ‘Something hit me in the back, but it’s not that bad.’

‘Name’s PT,’ the teenager said. ‘Hold on to me and we’ll be just fine. We’re probably less than a kilometre from the coast.’