For many centuries, people have practiced breath-hold diving. Evidence of this comes from many thousands of years’ old undersea artifacts that have been found on dry land. In Ancient Greece, breath-hold divers are well-known to have hunted and engaged in military activities under the sea.

It took the invention of apparatus to help humans breathe underwater before many people could see the world underneath the ocean—before the apparatus, each dive was short, frantic and dangerous.

Breath-hold Diving

Breath-hold diving is the very earliest form of diving and is still used heavily for commercial and sport purposes. The breath-hold divers’ compressible air spaces are squeezed by the increased water pressure throughout the dive. Each dive is limited by the individual’s tolerance for breath-hold and the ever-growing risk of drowning from hypoxia—which is always a minute or less away.

Diving in a Heavy Walled Vessel     

Heavy-walled vessels can maintain their internal atmosphere at or near sea level pressure, and so prevent the surrounding water pressure from affecting the occupants of the vessel. The submarine is probably the most famous heavy walled vessel, but the bathysphere is also very popular. The bathysphere is a hollow steel ball that can be lowered from a ship by a steel cable. With a diver in an atmosphere suit, they can work at great depths for many hours.

Diving With a Compressed Air Supply

The diver is separated from his source of fresh air—which is normally kept at the surface on a boat. Air reaches the diver through a long umbilical which ends in a mouthpiece carried by the diver. In more advance suits, the umbilical actually connects to the diver’s suit. This kind of diving has the diver breathing air at the same pressure as the water that surrounds him, which can lead to the bends and air embolisms.

Scuba Diving

Scuba diving is one of the most popular forms of diving. This is where the diver takes his source of oxygen with him on his back. There are many variations to this—but divers are still at risk for decompression problems like the bends and the need to be careful.