Sources
Hadal is a fictional expedition. The submersible and crew are invented; the depths, measurements and animals are real. Here is where each fact on the dive comes from.
NOAA JetStream
The five depth zones and their boundaries: 200, 1,000, 4,000 and 6,000 metres.
Used in the sunlight zone, the twilight zone, the midnight zone, the abyssal zone and the hadal zone.
NOAA National Ocean Service
The ocean's average depth (3,682 m) and the depth of the Challenger Deep.
Used in the midnight zone and the floor.
Revised depth of the Challenger Deep from submersible transects
Greenaway, Sullivan, Umfress, Beittel and Wagner, Deep-Sea Research I (2021)
The depth we dive to: 10,935 m, give or take 6 m.
Used in the floor.
Deep and bottom currents in the Challenger Deep, Mariana Trench
Taira, Yanagimoto and Kitagawa, Journal of Oceanography (2005)
Water temperature at the bottom of the trench, about 2.5 °C.
Used in the hadal zone and the floor.
How much oxygen comes from the ocean?
NOAA National Ocean Service
Roughly half of the oxygen produced on Earth comes from ocean plankton.
Used in the sunlight zone.
NOAA National Ocean Service
The layer where warm surface water gives way to the cold deep ocean.
Used in the sunlight zone.
NOAA Ocean Exploration
About 80% of animals living between 200 and 1,000 metres make their own light.
Used in the twilight zone.
A brief view of open ocean midwater ecology
NOAA Ocean Exploration
Lanternfish, their light organs, and the nightly rise of midwater animals.
Used in the twilight zone.
The University of Tokyo
The anglerfish's lure (the esca) glows with light-producing bacteria.
Used in the midnight zone.
NOAA National Ocean Service
What marine snow is made of, and that some flakes fall for weeks.
Used in the abyssal zone.
Hakai Magazine (on Jamieson and Vecchione, Marine Biology, 2020)
Dumbo octopuses filmed at 6,957 m in the Java Trench, the deepest octopus seen.
Used in the abyssal zone.
New fish species lives 5 miles underwater, a record
National Geographic (on Gerringer et al., Zootaxa, 2017)
The Mariana snailfish, described in 2017 and filmed at 8,178 m.
Used in the hadal zone.
Scientists break new record after finding world's deepest fish
The University of Western Australia (2023)
The deepest fish ever filmed, a snailfish at 8,336 m, and the likely limit for fish.
Used in the hadal zone.
NOAA Ocean Exploration (2021)
Hadal trenches form where tectonic plates meet, and are among the least explored places on Earth.
Used in the hadal zone.
Lucky day: Navy celebrates 60th anniversary of deepest ocean dive
US Office of Naval Research (2020)
Trieste's dive in 1960: Don Walsh and Jacques Piccard, nearly five hours down, 20 minutes at the bottom, a steel crew sphere the size of a refrigerator.
Used in the floor and the vessel page.
James Cameron returns from deepest ocean dive
National Geographic (2012)
Deepsea Challenger, the first solo dive to the Challenger Deep, and its 2 hour 36 minute descent.
Used in the vessel page.
DNV
Limiting Factor's titanium hull, designed for 1,127 bar and certified for repeated dives to full ocean depth; its 2019 dive to 10,925 m.
Used in the vessel page.
How the gauge works it out
Pressure rises by about one atmosphere for every ten metres of seawater. Water gets very slightly denser as it is squeezed, so the gauge uses a rate tuned to the measured pressure at the bottom of the Challenger Deep, about 1,086 bar (1,072 atmospheres). Readings in between are within about one per cent.
Temperatures follow a typical profile for the tropical western Pacific: about 29 °C at the surface, a steep drop through the thermocline, about 4 °C at 1,000 m and 1.5 °C in the abyss, then a slight rise to about 2.5 °C at the bottom. Real readings change with the seasons and the weather.
The animals on the dive are placed at depths where they have been found, but most range much more widely than one point on a page.