Doug Allan

Just six months ago, the last trial of this compressed-air diving lung failed thanks to issues with the exhaust mechanism.

But the group are hopeful that those glitches have now been fixed.

In the water, Cousteau sinks gently and takes a tentative breath.

A faint whistle greets his inhalation, and a ripple of bubbles escapes as he lets it out.

The equipment is working.

He is breathing underwater.

It has been done before, but in previous trials there was always a hitch when the diver moved.

This time, however, it feels different.

Cautious at first, he kicks slowly downwards, then up again.

The kit remains stable, even when he experiments with somersaults and barrel rolls.

As he swims, a canyon opens below him.

He marvels at the green weeds, black sea urchins, and flower-like white algae.

He sinks deeper than a mask and snorkel would ever allow him, taking his time in this underwater paradise.

Glancing up past a school of silvery fish, he sees the slender shape of Simone on the surface.

He waves, and the silhouette waves back.

With plenty left in the cylinders, he swims deeper towards a cave.

Once he's through the dark, narrow tunnel, it opens up, revealing a roof covered with lobsters, their heads and antennae pointing towards the entrance.

Cousteau plucks a pair from their rock face, then checks the tank.

It's time to head back to the surface.

Diving is hungry work, but now he has a hand-selected luxury supper to look forward to.