The average depth of the world’s oceans is 3,790 meters, or 12,400 feet, or 2 1⁄3 miles. There is no light, and the pressure is 370 atmospheres, or 5,400 pounds per square inch!
Pearl divers can work at 40 meters but at this depth there are serious health hazards other than drowning.
How Deep Can We Go?
The average depth of the Atlantic Ocean is 3,900 meters, or just over 2 miles.
At 10 meters a diver experiences twice the pressure he or she felt due to air at the surface. The water at this depth absorbs 80% of sunlight. 10 to 15 meters are depths that free divers, without air, can reach fairly easily.
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(Not to scale)
The average depth of the Caribbean Sea is 2,200 meters, or about 1.3 miles.
At one meter, 60% of visible light is already absorbed by clear seawater. Cloudy water would block even more sunlight and can cut visibility to almost zero.
A nuclear submarine can dive to a depth of about 300m. This one is larger than the research vessel Atlantis and has a crew of 134.
The research vessel Atlantis, shown at the surface, is 274 feet long. At this scale the divers and their small boat are almost invisible.
The Challenger Deep is the deepest known point in the Mariana Trench and is still believed to be the deepest point in the world’s oceans. In 1960 the bathyscaph Trieste, carrying two men, set a world record by diving to the bottom of it. The onboard systems indicated a depth of 37,800 ft (11,521 m) but this was later corrected to 35,813 ft (10,916 m) by taking into account variations arising from salinity and temperature. Later and more accurate measurements made in 1995 have found Challenger Deep to be shallower at 35,798 ft (10,911m).
WHOI’s submersible Alvin carries two scientists and a pilot as deep as 4,500 meters (about 3 miles) and each dive lasts six to ten hours. Built in 1964 as the world’s first deep-ocean submersible, Alvin has made more than 4,200 dives. It can reach nearly 65% of the global ocean floor.
If we can reach a depth of 4,000 meters, we can explore 63% of the world’s ocean floor. The nuclear submarine now looks like a shallow diving vessel. Luckily, the Atlantis on the surface can launch specialized vehicles for deep submergence exploration.
At 150m depth, 99% of light has been absorbed by clear seawater.
The pressure at 100 meters is more than 10 atmospheres, ten times the air pressure at the surface. Scuba divers can work at 100 meters if the are very cautious rising to the surface.