http://en.wikipedia.org/wiki/Pearl_hunting
For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in areas such as the Persian Gulf, the Red Sea, and in the Gulf of Mannar (between Sri Lanka and India). In a similar manner as in Asia, Native Americans harvested freshwater pearls from lakes and rivers like the Ohio, Tennessee, and Mississippi, while others successfully retrieved marine pearls from the Caribbean and waters along the coasts of Central and South America.
In the time of colonial slavery in northern South America (off the northern coasts of modern Colombia and Venezuela), a unique occupation amongst slaves was that of a pearl diver. A diver's career was often short-lived because the waters being searched were known to be shark-infested, resulting in frequent attacks on divers. However, a slave who discovered an extra-large pearl could sometimes purchase his freedom.
