By increasing the volume of air in his lungs, Nash floated free of the bottom. The silt soon dispersed in the current, leaving visibility at around an arm’s length. Rolling on his back, he found purchase on the thin welded ridges between the hull plates and manoeuvred his way around the twin rudders. Although still locked at forty-five degrees, they were undamaged. Behind the rudders were the twin propellers. Running his hands over the big bronze blades, Nash hoped Douglas was right and Boerman was nowhere near the start button.

What Kaboro had feared most was damage to the vulnerable propeller shafts. These ran exposed for three and a half metres before entering the hull and, if snapped or bent, meant a dry dock repair. Nash did his best to sight along the shafts and feel for distortion. It seemed the Albany had been lucky. Her stern had not connected heavily with the bottom during the collision, because her flat semi-displacement hull, which gave her speed, had helped her skip like a stone. Nash began to feel heartened; maybe they could get out of here under their own steam.

The close inspection work helped keep his mind off potential wildlife, and soon he reached the stabilisers. These rudder-like blades projected at a forty-five-degree angle, just below the waterline, to provide control when the boat was up and planing. Here, he discovered the leading edge of the port stabiliser had been dented for about half its length. While the damage was not catastrophic, Nash guessed it would create drag and affect handling, and he duly fired away with the GoPro.

Amidships, there was only superficial hull damage – dents, scratches and gouges. Nash continued until his tank bumped the mud below. As the silt billowed up, he was reminded of ‘gardening’ the dirt-filled tunnels under the limestone of Mount Gambier, South Australia – excavating spoil to access new routes. Get too enthusiastic and you could end up digging your own grave.

In the zero visibility, the edge of anxiety he’d been suppressing began to assert itself. A feeling of breathlessness came over him, and he was filled with a nagging sense of dread. It was time to call the dive. Exiting on the port side, Nash prayed no one up top mistook him for an inquisitive croc.

It felt bloody wonderful to reach the surface and feel the expanse of sky overhead.

‘How is she?’ Kaboro was leaning over the rail, having tracked his bubbles.

Sitting in the mud, Nash gave him a thumbs up. ‘No significant damage. But the leading edge of the port stabiliser is slightly bent.’ He held up his hands to demonstrate.

‘Seems we’ve been lucky, then.’