Japanese tradition holds that the practice of ama may be 2,000 years old. Traditionally, and even as recently as the 1960s, ama dove wearing only a loincloth. Even in modern times, ama dive without scuba gear or air tanks, making them a traditional sort of free-diver.
Ama can keep diving well into old age. The older divers are generally able to stay submerged longer than the younger. Usually they also have another job, typically working on a farm. The Japanese believe that the majority of ama are women because of how their bodies differ from men: The fat on a female body is distributed differently than on men, which ensures that they can stay warmer in colder water.