And, like thousands of other children in the impoverished and war-shattered Gaza Strip, his family badly needs the money. The job is comparatively lucrative, with children getting up to 30 dollars for a 12-hour shift.
"I have six brothers. I'm the breadwinner for the family," says Anwar.
He says he doesn't mind not getting an education.
"School is useless."
Asked about the Israeli offensive that killed more than 1,400 Palestinians and devastated Gaza, Anwar shrugs. "The worst thing about the war is that I spent all my savings from working the tunnels."
Warplanes heavily bombed the Rafah border area during the 22-day war that ended on January 18, and again on several occasions since, targeting the tunnels that defy Israel's crippling blockade of the overcrowded coastal strip.
"We bring in anything you can imagine. Food, shoes, toys, refrigerators, ovens. Even cars -- they take them apart, cut them in half and put them together again in Gaza," says Anwar.
Israel says Hamas, Gaza's Islamist rulers, also uses tunnels to bring in the rockets and mortars they fire at Israel.
Anwar insists the tunnel in which he worked brought in only commercial goods. "Never weapons, the government has special tunnels for that."
He says he doesn't worry about the Israeli air strikes. "The Jews are our enemy. I'm not scared of them."
-- 'He's just a kid' --
Tunnel operators say Egypt too is increasingly cracking down on the underground smuggling, pumping sewage or gas, or throwing explosives into the tunnels.
"Three people died in the tunnels around here this week," said one man who would only identify himself as Mohammed, standing by a 10-metre-deep (about 30 feet) shaft at the entrance of his tunnel.
Tents or brick shacks cover the entrances of dozens more tunnels around his stake. A watchtower overlooking this "tunnel city" marks the Egyptian border, about 200 metres (yards) away.
"The tunnel was destroyed five times from the Egyptian side," says Mohammed, as workers inside the tunnel pile earth and rubble onto a trolley attached to a generator-run electric pulley.
He denies employing child labour, though the vast majority of the tunnels owners do employ youngsters.
A recent study by the Palestinian Centre for Democracy and Conflict Resolution (PCDCR) showed that more than half the 16,000 people working in the tunnels are under 18, as were 30 of the 115 people killed in the tunnels since Israel imposed the blockade two years ago.
The Hamas government says the tunnels are legal until the blockade is lifted and the Rafah municipality charges a 10,000 shekel (2,500 dollar/1,800 euro) fee to open one.
But what is illegal under Palestinian law is to employ children under the age of 16, says Iyad Abu Hujaier of the PCDCR.
Tunnel work is both dangerous and exhausting.
"I was in the middle of the tunnel. Egypt put some gas in. Three workers died, 18 were treated for suffocation," says 14-year-old Osama.
"I decided not to go again, but my father died so I was forced to go back for about one month," says Osama, who is spending much of the summer school holiday at a youth centre financed by the UN children's agency UNICEF.
His 15-year-old friend Mohammed is adamant: "I won't go back to the tunnels, it's horrible in there."
Hujaier says most of the children who work in the tunnels use Tramadol -- also known as Tramal -- a painkiller said to produce a mild high and to relieve anxiety.
For the families, he says there is no alternative to the child labour, they desperately need the money.
"When we tell parents 'he's just a kid and needs to enjoy his childhood' they look at us like we come from the moon, they make us feel like we're not being realistic."
As long as the Israeli blockade remains, "this crisis will continue, the tunnels will continue and children will continue working in the tunnels," says Hujaier.
Anwar is also convinced the tunnels are here to stay. "When I grow up I want to be a professional tunnel digger, because you make a lot of money."
--------------------------------------------------------------------------------------------------------------------------