From the coast of Bangka Island in Indonesia, miners like Hendra travel off the coast every day to build a fleet of crude wooden pontoons equipped with equipment for dredging the seabed to obtain lucrative tin ore deposits.

Indonesia is the world’s largest exporter of tin, used in everything from food packaging to electronics and now green technology.

However, the deposits of Bangka Belitung Mining Center have been extensively mined on land, making some islands near the southeast coast of Sumatra resemble a lunar landscape, with huge craters and highly acidic turquoise lakes.

The miners are turning to the sea.

“On land, our income is declining. There are no more reserves,” said Hendra, 51, who switched to offshore tin mining after 10 years in the industry about a year ago.

“In the ocean, there are much more reserves.”

The crumbling pontoon camps are usually gathered around the tin seams on the seabed, and the diesel generators emit black smoke and the roar is so loud that workers can only communicate with gestures.

Hendra uses a name like many Indonesians and operates six pontoons, each operated by three to four workers, and the pipes are 20 meters (66 feet) long and are used to suck sand from the seabed.

The pumped mixture of water and sand flows through a plastic mat, which is sandwiched with sparkling black sand containing tin ore.

Hendra is one of dozens of artisanal miners working with PT Timah to develop a state-owned miner concession.

Hendra said that for every kilogram of tin sand mined by miners, they can get about 70,000 to 80,000 rupees (4.90 to 5.60 U.S. dollars), and a pontoon usually produces about 50 kilograms per day.

Timah has been increasing offshore production. According to company data, last year’s proven land tin reserves were 16,399 tons, while offshore tin reserves were 265,913 tons.

The large-scale expansion, coupled with reports that illegal miners are targeting offshore deposits, has intensified tensions with fishermen. They said that since 2014, their catches have been drastically reduced due to the continuous encroachment of their fishing grounds.

Apriadi Anwar, a fisherman, said that in the past, his family income was enough to pay for his two younger siblings to go to college, but in recent years they have barely made ends meet.

“Don’t even go to university, now it’s hard to even buy food,” said 45-year-old Apradidi, who lives in Batu Perahu village.

Apriadi said that fishing nets may be entangled with offshore mining equipment, while trawling the seabed to look for ore joints that polluted the once pristine waters.

“Fishes have become scarce because the corals where they spawn are now covered by mud from mining,” he added.

The Indonesian environmental organization Walhi has been committed to stopping offshore mining, especially on the west coast of Bangka, where the mangrove forests are relatively well-preserved.