Ten stops between the surface and the deepest surveyed point in the ocean. One depth per slide. The pressure, the light and the animals are real.
10 metres · 2 atmospheres
Ten metres of seawater weighs as much as the entire atmosphere above it. The pressure on your body doubles before you have gone the length of a bus.
NOAA Ocean Exploration, pressure in the deep ocean: one atmosphere per 10 m.
Five times the pressure you were born into, pushing on every surface of you.
Where nitrogen under pressure begins to work on the mind like a drink. Divers call it narcosis.
The line the certifying agencies draw. Past it you need other gases, and other training.
PADI recreational limits; US Navy Diving Manual on nitrogen narcosis.
200 metres · 21 atmospheres
By 200 m about one per cent of the sunlight is left. Below this line there is too little for anything to photosynthesise. The ocean stops being a garden.
NOAA Ocean Exploration, ocean zones: the sunlit zone ends near 200 m.
Ahmed Gabr, Red Sea, 2014. The descent took twelve minutes. The return took most of a day, in stops that lengthen toward the surface, so the gas dissolved in his blood could leave it slowly enough not to foam.
Guinness World Records, deepest scuba dive, 332.35 m, 12 min descent. Stop schedule drawn schematically; totals as recorded.
1,000 metres · Midnight zone · 101 atmospheres · 4 °C
No sunlight reaches here at all. In a survey of the animals of the open water off California, three in four made their own light.
Martini & Haddock, Scientific Reports, 2017.
2,992 metres · 300 atmospheres
A Cuvier’s beaked whale, tagged off California, reached this depth on one breath and stayed under for more than two hours. The deepest dive recorded for any mammal.
Schorr et al., PLOS ONE, 2014.
3,800 metres · Midnight zone
Found in 1985 after seventy-three years in the dark, in two pieces, on a bed of silt. Iron-eating bacteria are slowly turning the hull into rust icicles.
Woods Hole Oceanographic Institution; NOAA Office of Ocean Exploration.
The deepest fish ever filmed: a snailfish in the Izu-Ogasawara Trench, Japan, 2023.
Minderoo-UWA Deep Sea Research Centre with Tokyo University of Marine Science and Technology, 2023.
10,935 metres · Challenger Deep · 1,094 atmospheres
The bottom. Jacques Piccard and Don Walsh reached it first on 23 January 1960, in a steel sphere named Trieste, and stayed twenty minutes after a window cracked on the way down.
Nobody has gone deeper, because there is no deeper to go.
Sources
NOAA Ocean Exploration: ocean zones, pressure, Challenger Deep.
Guinness World Records: deepest scuba dive (Gabr, 2014).
Martini & Haddock, Sci. Rep. 7, 2017: bioluminescence survey.
Schorr et al., PLOS ONE 9(3), 2014: Cuvier’s beaked whale dives.
Woods Hole Oceanographic Institution: Titanic, 1985 discovery.
UWA / TUMSAT, 2023: snailfish at 8,336 m.
US Navy: bathyscaphe Trieste, 1960.