People have strong attention in going beneath the sea for centuries. Ancient script coins ntadelineation of early divers. Century old artifacts imply that people dove for materials for jewelry such as pearls. Greek literature refers to early sponge divers. Herodotus (500 B.C.) tells the story of Scyllis, a Greek sailor, who used a reed to breathe as he cut the mooring lines of Persian ships. This interest pushed people to develop ever-improving methods of staying underwater for longer periods of time and at ever increasing depths.
Men and women have practiced breath-hold diving for centuries. Indirect evidence comes from thousand-year-old undersea artifacts found on land (e.g., mother-of-pearl ornaments), and depictions of divers in ancient drawings. In ancient Greece breath-hold divers are known to have hunted for sponges and engaged in military exploits. Of the latter, the story of Scyllis (sometimes spelled Scyllias; about 500 BC) is possibly the most celebrated. As told by the 5th century BC historian Herodotus (and quoted in numerous modern texts).
The aspiration to go underneath water has probably always existed: to hunt for food, uncover artifacts, repair ships (or sink them!), and perhaps just to observe marine life. Until humans found a way to breathe under water, however, each dive was necessarily short and frantic.
Under water we can Breathing through a hollow reed allowed the body to be submerged, but it must have become perceptible right away that reeds more than two ft long do not work well; impenetrability inhaling against water pressure effectively limits snorkel length. Breathing from an air-filled bag brought under water was also tried, but it failed due to rebreathing of carbon dioxide.
In the 16th century people began to use diving bells complete with air from the surface, most likely the first effective means of staying under water for any length of time. The bell was held stationary a few ft from the surface, its bottom open to water and its top portion containing manner dense by the water pressure. A diver standing upright would have his head in the air. He could leave the bell for a minute or two to collect sponges or explore the bottom, and then return for a short while until air in the bell was no longer breathable.
In 16th century England and France, full diving suits made of leather were used to depths of 60 ft. Air was pumped down from the surface with the aid of manual pumps. Soon helmets were made of metal to withstand even greater water pressure and divers went deeper. By the 1830s the surface-supplied air helmet was perfected well enough to allow extensive salvage work.
Starting in the 19th century, two main avenues of investigation - one scientific, the other technologic - greatly accelerated underwater exploration. Scientific research was advanced by the work of Paul Bert and John Scott Haldane, from France and Scotland, respectively. Their studies helped explain effects of water pressure on the body, and also define safe limits for compressed air diving. At the same time, improvements in technology - compressed air pumps, carbon dioxide scrubbers, regulators, etc., made it possible for people to stay under water for long periods.