Bearing torches that lit up the night as they swam out into the ocean, Japan's storied ama prayed for an abundant catch in a ceremony that has been held by these female free divers for decades.

This year, however, most of the 80 white-clad participants in the weekend event in Minamiboso, Chiba Prefecture, were volunteers, as age and disinterest have reduced the number of women willing to make a livelihood out of this type of diving in this fishing community.

Japan is home to the world's oldest population, and the number of female ama, a Japanese word meaning sea-diving fishers, fell to just 40 last year in the Shirahama district in Minamiboso, down 70% from 2006, according to a local fisheries cooperative.