He is among the hundreds of boys who collect coins thrown into the river by visitors and devotees during the annual month-long Sonepur fair, which is said to be Asia's biggest cattle fair.
Armed with heavy magnetic rings tied with colourful plastic ropes, Rohit is at work every day from 5am to 5pm. For a month, he is missing school.
"I fish out around 100 rupees [$1.83; Â£1.14] to 110 rupees every day and my mother is happy with my efforts," says Rohit.
His father, Shatrughan Singh, is a day labourer who earns a similar amount on the days he can find work.
Rohit hands over the money he collects to his parents and it goes a long way in helping feed their family of six.
Rohit first started going to the river bank two years ago after he saw other village boys going every morning with their fishing lines.
"I was curious, so one day I went along with them and learned the tricks of the trade," he said.
He borrowed 10 rupees ($0.18; Â£0.11) from his mother, promising to return double the money in the evening.
At the beginning of the cattle fair, hundreds of thousands of Hindu devotees bathe at the confluence of the Gandak and Ganges rivers in Sonepur, in Saran district, 35km (21 miles) north of the state capital, Patna.
The devout also throw coins in the river as a mark of their devotion and reverence.
As soon as a coin is thrown into the water, the hawk-eyed little boys throw their magnets in the same direction, much like the fishermen throwing their nets into the sea.
"I generally collect coins worth 150 rupees ($2.70; Â£1.70) a day and most of the time my family buys food with this money," said Rakesh Kumar, another coin collector.
Rakesh's father, Suresh Rai, runs a tea stall at the fair ground and has a large family of nine members.
Rakesh and his sibling Bittu Kumar come to the river bank every morning at the crack of dawn and leave only after at 5pm.
"My rope has just a single magnet which is not very effective. I'll buy a bigger one soon so that I can collect more coins," Rakesh said.
Gruelling poverty
His friend Krishna Kumar, who also collects coins worth 100-150 rupees a day, says their work is not easy.
"I spend almost 10 hours a day on the river bank, with my eyes fixed on the coins thrown into the water. Sometimes I get them, sometime I lose to other friends," he said as he displayed a coin he had just fished out of water.
Krishna says he keeps a part of the money he makes "to buy some sweets at the fair".
"When the fair begins, one can see hundreds of young coin collectors here. See how they have used local technology to fish out coins from water," Radheshyam Panda, who performs religious rituals on the river bank, said.
"These young coin collectors may use different magnet sizes or different colours of plastic ropes but one thing which they have in common is their gruelling poverty," said Mahendra Babu who sells ingredients for religious ceremonies on the river bank.
Every day since 28 November, 10-year-old Rohit Kumar has sat from dawn to dusk on the banks of the Gandak river in the eastern Indian state of Bihar with a magnetic fishing line trying to fish out coins from the water.