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It's July, 1977. A bright summer's day shines across the Great Glen in the Scottish Highlands, a deep,

ancient valley formed during the Ice Age.

Wild, rugged mountains tower into the broad skies above.

The sun glows across the greens and yellows of the steep wooded hillsides and

dances on the surface of the world's most famous lake, Loch Ness.

The wind is gentle today, and the water seems calm and clear to the tourists walking and sailing along the northern shore.

But moving downwards, beneath the surface, the water quickly becomes murky and dark, stained black by the surrounding peat.

In places, the immense lake drops down 750 feet, shrouded in mystery. Deep in the

lock, swimming far beyond the sun's reach, 24-year-old Hugh Williams is exploring. His orange

neoprene dry suit protects him from the icy temperatures.

He drifts through the water, slowly paddling his legs, scanning left, then right.

Complete darkness surrounds him, save for a sharp beam of light that he angles from his lamp.

The only sounds he can hear are his steady breath through his diving mask

and the loud, rhythmic thud of his heart.

Below ten meters and you're in pitch darkness.

And when I say pitch darkness,

...