Before the beginning of the 20th century, pearls were obtained from pearl oysters. These oysters were collected from the bottom of the ocean, lake or river.

To get enough pearl oysters, free-divers were often forced to descend to the depth of more than 100 feet in one breath. Because of the difficulty of diving, pearls at that time were of different quality as well as very rare.

In Asia some pearl oysters could be found on shoals at a depth of 5–7 feet from the surface. At times the divers had to go 40 feet or even up to 125 feet deep to find enough pearl oysters. These deep dives were extremely hazardous to the divers.