Japanese tradition holds that the practice of ama may be 2,000 years old. Traditionally, and even as recently as the 1960s, ama dived wearing only a loincloth. Even in modern times, ama dive without scuba gear or air tanks, making them a traditional sort of free-diver.
They are topless because they stay down for two minutes at a time without modern diving gear. It's much easier to swim deep for hours with less clothes than more clothes. It's also traditional. This isn't like western topless beaches. Going topless here is for practical work efficiency. These days the Ama use wetsuits and masks. Virtually all Ama are very old now and few remain.
