What they are escaping is a broken country where half the people are going hungry, most schools and hospitals are closed or dysfunctional and a cholera epidemic has taken a toll in the thousands. Yet they are arriving in a place where they are unwelcome and are resented as rivals for jobs. Last year, Zimbabweans were part of the quarry in a spate of mob attacks against foreigners.

For those in the know, crossing the border can be a simple chore, a bribe paid on one side and a second bribe on the other. But for the uninitiated and the destitute, the journey is as uncertain as the undercurrents of the Limpopo and the appetites of the crocodiles.

Where is it best to enter the river? Where are the holes in the barbed fences beyond? Where do the soldiers patrol? Perhaps the greatest risk is the gumagumas  the swindlers, thieves and rapists who stalk the vulnerable as they wander in the bush.

Williad Fire, 16, who arrived here on Jan. 4, is one of nine boys who came from Murimuka, a town in a mining region of central Zimbabwe. His story is a fairly typical one of serial catastrophe. He was living with an uncle after his parents died, but then the uncle died, too, stricken in November with an illness that Williad described with a mystified shrug: “He was vomiting blood.”

Image Musina has 57,000 residents, plus 15,000 foreigners. Credit... The New York Times

The boy was hungry, and scrounging in South Africa seemed to hold more promise than scrounging at home. To get train fare south, he sold his most valuable possession, a secondhand pair of Puma sneakers two sizes too big. He and eight friends then did odd jobs in Beitbridge, on the Zimbabwean side of the border, until they had saved about $35.