'It is quiet and cool and dark blue. At this depth the pressure on my body is double what it is at the surface: my heartbeat has slowed, blood has started to withdraw from my extremities and move into the space my compressed lungs have created. I am ten metres underwater on a breath-hold dive, suspended at the point of neutral buoyancy where the weight of the water above cancels my body’s natural flotation. I turn head down, straighten my body, kick gently, and begin to fall with the unimpeded gravitational pull to the heart of the Earth.' (Introduction)
