Leaving the warm, blue waters of the upper ocean behind, we are descending into the deepest, most inhospitable habitat on Earth.
This is the abyssopelagic zone, or the abyss.
The abyss begins 4000m down. Locked in darkness and with crushing pressures, this is the largest and most mysterious biome on Earth.
Depth: 4000m to 6000m
Amazingly, there is life here. Animals such as the brittle star and tripod fish feed on nutrients in the sediment.
While scavengers feed on fallen carcasses.
Within the abyss is the largest mountain range on Earth – the mid-ocean ranges, spanning around 50,000km.
Depth: 2500m to 4000m
Height: can reach 3.2km
Hydrothermal vents eject ferociously hot water, containing poisonous gases, into the surrounding ocean.
Release hydrogen sulphides
Remarkably, entire ecosystems surround these chimneys. Bacteria can turn the harmful gases into energy, supporting hundreds of species, including tube worms, mussels, white crabs, and Pompeii worms, which survive in water temperatures of up to 80 degrees centigrade.
The abyssal plain is broken by colossal trenches. The Mariana trench is the largest of these. It could easily swallow Mount Everest.
Western Pacific Ocean
Within these depths is the hadalpelagic zone, the deepest of all ocean habitats.
Depth: 6000m to 11000m
Animal life is rare, but includes shrimp and jellyfish, which feed on marine snow – fallen organic particles from the richer oceanic habitats above.
More people have travelled into space than have visited the abyss. With every dive, new discoveries are made in this vast alien world.