John Hopkins

Finally he slows, his tight grasp on the lifeline still intact.

Taking a moment and regaining some of his clarity, he is able to look at the dive computer attached to his wrist, which tells him his depth.

Somehow, in his barely lucid, discombobulated state, he has still managed to travel upwards along the rope.

But he is at 35 meters.

He has gone too high too quickly.

He has to get his decompression schedule back on track.

Moving carefully, Don retreats down the line to 46 meters.

Now totally unable to focus properly on his rebreathers controls, his safest option is to stay on his backup open circuit tanks.

But this will burn through his air supply, and with the time consuming ascent still ahead of him, he's going to need more gas.

Don reaches out for a cluster of cylinders, clipped to the line nearby.

As he does so, his stomach does a somersault.

When he is finally able to, he gingerly starts grappling his way up the line towards the next decompression stop.

Above, a figure moves down towards him.

A support diver is coming to check on his progress.

Rapidly, the news reaches the surface team.

Don needs urgent aid.

A tether is made to clip him to the shot line in case he loses consciousness, and a rotor is agreed to ensure at least one diver remains with him at all times.

But despite this, Don's situation remains dire.

It's been a couple of hours since he entered the water, but as he nears the surface, his decompression stops need to become longer and more frequent, meaning he still has more than 10 hours to go.

The climb is grueling.