"Kino had two ropes, one tied to a heavy stone and one to a basket. He stripped off his shirt and trousers and laid his hat in the bottom of the canoe. The water was oily smooth. He took his rock in one hand and his basket in the other, and he slipped feet first over the side and the rock carried him to the bottom. The bubbles rose behind him until the water cleared and he could see. Above, the surface of the water was an undulating mirror of brightness, and he could see the bottoms of the canoes sticking through it."
The Pearl - page 22
Pearl diving has been performed for centuries, we have records back to about four thousand years ago, in the Persian Gulf the Summarians had practiced pearl diving. Approximately two thousand years ago the Japanese had begun to hunt for pearls, their divers were mainly women, they were believed to be better divers and were refered to as ''amas'' which translates to sea woman. The australians in the early seventeenth century had also presented the pearl industry.
The reality in today's society where pearl diving (also known as pearl hunting) exists, it consists of diving into deep waters populated by pearl producing oysters or freshwater pearl mussels, followed removing them from the bottom of the sea to examine them and extract a pearl, they are very rare usually. The matter of the fact is we find three or four high quality pearls among an entire ton of oysters. This also supports the reasoning for their great expense. However, a large majority of pearl hunting today is based on exploration and hobby rather than financial interest, mainly because most pearls aren't harvested naturally.
http://www.divingheritage.com/pearldivingkern.htm
http://www.ehow.com/about_6643483_pearl-diving.html