How does diving technology work?

The answer depends on the type of diving referred to in the question. Shallow-water diving, e.g., SCUBA (Self-Contained Underwater Breathing Apparatus), is far less complex than deep-sea diving. It requires only a tank of air and a mouthpiece for breathing.

As the depth of the water increases, other factors such as water pressure arise. Including standard atmospheric pressure at sea level, the water pressure in salt water at a given depth can be approximately calculated by this equation (depth in feet, pressure in pounds per square inch - PSI):

PSI = 14.7 + 0.434 x depth (ft)

Example: at 100 ft of depth, 14.7 + 0.434 x 100 = 58.1 PSI.

The records for "open circuit" (no rebreathers used) SCUBA diving is 1083 feet, set in 2005 by a fit, well-trained diver. That depth would kill the average diver.

Another factor is decompression sickness, commonly called "the bends". This is caused by a diver ascending too quickly from a high-pressure depth to atmospheric pressure. Inert gases such as nitrogen that are absorbed by body tissues expand and create bubbles as the pressure decreases. If done too quickly, its effects can range from joint and muscle pains to death (rare, but...).

Below a certain depth, the diver needs to be encased in an artificial environment. The atmospheric diving suit is essentially a personal sumbersible that totally isolates the diver from the water, allowing dives to 2000 feet or more. Pressure-wise, 200 feet = 882 PSI, which would crush an unprotected person. The suits operate at atmospheric pressure, ergo eliminating decompression and allowing normal air to be used.

Since the usual public image of diving is SCUBA, the technology is fairly simple, as long as the necessary maintenance and safety procedures are zealously followed.