Pre-industrial:

• Several centuries BC: (Relief carvings made at this time show Assyrian soldiers crossing rivers using inflated goatskin floats. Several modern authors have wrongly said that the floats were crude breathing sets and that they show frogmen in action.)
• Ancient Roman and Greek times, etc.: There have been many instances of men swimming or diving for combat, but they always had to hold their breath, and had no diving equipment, except sometimes a hollow plant stem used as a snorkel. See this link (in Portuguese).
• About 500 BC: (Information originally from Herodotus): During a naval campaign the Greek Scyllis was taken aboard ship as prisoner by the Persian King Xerxes I. When Scyllis learned that Xerxes was to attack a Greek flotilla, he seized a knife and jumped overboard. The Persians could not find him in the water and presumed he had drowned. Scyllis surfaced at night and made his way among all the ships in Xerxes's fleet, cutting each ship loose from its moorings; he used a hollow reed as snorkel to remain unobserved. Then he swam nine miles (15 kilometers) to rejoin the Greeks off Cape Artemisium.
• The use of diving bells is recorded by the Greek philosopher Aristotle in the 4th century BC: "...they enable the divers to respire equally well by letting down a cauldron, for this does not fill with water, but retains the air, for it is forced straight down into the water."^[2]
• 1300 or earlier: Persian divers were using diving goggles with windows made of the polished outer layer of tortoiseshell.
• 15th century: Leonardo da Vinci made the first known mention of air tanks in Italy: he wrote in his Atlantic Codex (Biblioteca Ambrosiana, Milan) that systems were used at that time to artificially breathe under water, but he did not explain them in detail due to what he described as "bad human nature", that would have taken advantage of this technique to sink ships and even commit murders. Some drawings, however, showed different kinds of snorkels and an air tank (to be carried on the breast) that presumably should have no external connections. Other drawings showed a complete immersion kit, with a plunger suit which included a sort of mask with a box for air. The project was so detailed that it included a urine collector, too.
• 1531: Guglielmo de Lorena dives on two of Caligula's sunken galleys using a diving bell from a design by Leonardo da Vinci.
• Around 1620: Cornelius Drebbel may have made a crude rebreather: see Rebreather#History of rebreathers.
• 1772: Sieur Freminet tried to build a scuba device out of a barrel, but died from lack of oxygen after 20 minutes, as he merely recycled the exhaled air untreated.
• 1776: David Bushnell invented the Turtle, first submarine to attack another ship. It was used in the American Revolution.