Like his father and grandfather before him, Phool dev Shahni once made a living by diving to the bottom of 8ft-deep (2.4m), muddy ponds.

“I used to dive in 7 to 8ft of water for hours a day – coming to the surface to breathe after 8 to ten minutes,” explains Mr Shahni.

While down in those murky depths he was harvesting the seeds of a type of water lily called euryale ferox.

Known as makhanas, fox nuts or lotus seeds, they are prized for their nutritional value, being high in B vitamins, protein and fibre, with some touting them as a superfood, external.

Often eaten as a snack, makhanas are also used in various dishes, including the milk pudding kheer, as well as being ground into flour.

In the north-western Indian state of Bihar, where Mr Shahni lives, 90% of the world’s makhana is grown.

The leaves of the lily plant are large and circular and sit on the top of the pond. But the seeds form in pods under water and collecting them was an exhausting process.

“While we are at the bottom diving, mud enters our ears, eyes, nose and mouth. Lots of us have skin issues due to this. Also the plant is covered in thorns, which give us cuts all over our body during harvesting of the seeds,” Mr Shahni says.

But in recent years farmers have changed the cultivation process. The plants are now often grown in fields, in much shallower water.

Harvesting seeds in just a foot of water means Mr Shahni can make twice as much money in a day.

“It’s still hard work but I am proud of my tradition. I have three children and I will make sure that one of my sons continues the legacy of working in a fox nut field.”