JAMBIANI, Zanzibar As the tide recedes, sand flats emerge from the azure sea and the once-deserted beach buzzes with activity. There is a new moon its bamvoua, the time with the low tides in the local dialect of Kiswahili.

Women wearing colorful fabrics called kanga hold baskets as they forage in sandy tide pools and children fish in the shallows with nets and lines. But further out, far beyond the rest, a group of women walk holding snorkels, masks, mesh bags and knives. They smile and chat as they dodge spiny sea urchins on their 20-minute trek through fine, sticky sand to tend to their submerged farms.

Historically, this area was dominated by seaweed farms there are thousands of seaweed farmers between Jambiani and Kenya to the north, many of them providing rare jobs for women but climate change has made growing seaweed increasingly difficult as water temperatures in shallow lagoons become too hot for seaweed to survive.

For these women wading out to sea, a novel, more profitable and resilient crop has emerged: sponges. There are only a handful of sponge farms in the world, mostly in the Federated States of Micronesia and other Pacific countries . These sponge farms on the southeast coast of Zanzibars Unguja Island are the first in the West Indian Ocean.

All 11 sponge farmers in the coastal town of Jambiani are women, most of them single mothers. The women own and run their own farms following a yearlong training set up by local conservation nonprofit Marinecultures, and they earn up to five times more than seaweed farmers. The work not only empowers them as they contribute to the local economy but it also gives them the independence to live in an increasingly expensive region and step out of womens traditional roles on the Muslim island.