TOPSHOT - A pair of young boys play in the Rio Grande in Piedras Negras, Mexico, on July 4, 2019. - Many parts of the river in Mexico used to be open to the public where many would go to swim or fish but due to an increase in illegal crossings by undocumented migrants, the Mexican Federal police now has closed off areas and patrols to keep people out. (Photo by Sergio Flores / AFP)