They began work in chest-deep water. Sinking to his knees, Nash turned on the powerful jet and began excavating the face of the bank. The dislodged mud rolled downhill to disperse in the deeper water. The full-face mask with a built-in demand valve helped distance him from the viscous soup. Time soon became meaningless, and in a sensory environment dominated by touch, the quickest way to check progress was by sliding a hand along the newly exposed hull. It took them two hours to carve trenches right up to the bow – each a metre deep and half as wide.

‘It won’t be enough,’ Boerman observed as they rehydrated on the bank. ‘We have to get right underneath to break the suction.’

Nash suspected he was right. However, the idea of tunnelling beneath the flat-bottomed hull in a muddy coffin-sized cavity was appalling.

Boerman’s big teeth gleamed whitely. ‘What’s the matter, Nash? Scared of a little mud?’

Nash was damned if he was going to let the Afrikaner get under his skin.

‘OK, we’ll try it. But we work from the keel to the outside only. Got that? From the keel to the outside.’

‘Ja, I heard you the first time.’

They reconvened under the midline of the Albany, in zero visibility, a tactile meeting of shoulders. Nash constantly checked his orientation so as not to sweep in Boerman’s direction. It was difficult, dangerous work, but by maintaining a generous excavation, Nash kept the claustrophobia at bay.

They carved away for perhaps an hour, and then Nash began to wonder just how much friction the remaining mud was exerting on the mass of the ship. He had already burrowed a good two body lengths into the bank; at some point the law of gravity would have to take over, and anyone caught underneath when the Albany slid into deeper water would become a smear of red paste.

Nash backed up to their starting point. Here, a narrow wall of mud demarcated their twin excavations. To his dismay, he discovered Boerman’s was barely forty centimetres deep, and as a result, the crazy Afrikaner had burrowed in much further towards the bow. Gritting his teeth, Nash slithered inside and felt around for Boerman’s oversized feet. There was no sign of him, just the hissing roar of his jet.

Damn the man.

He would have to go further inside.

Nash proceeded forwards on his belly, and as the excavation grew shallower, he wondered how on earth Boerman had even managed to fit in here. Then, with the hull hard against his back, the claustrophobia pounced.

The sense he was moments from suffocating was overpowering. In the full-face mask, he heard a voice keening in fear and was horrified to realise it was his.

‘Idiot!’ he chastised himself.

What he needed to do was kill the pumps. That would drive the bastard out.