“The river in that area has brush-filled and dried-out riverbed which makes it “very easy” for people to be confused as to what side of the border they are on.”
Yet another reason to have a wall ... or where a wall is not feasible or not built yet — there should at least be border markers along the entire border that indicate the boundary between the two countries. This is ridiculous.
In this case they were south of the wall but north of the border, which is the river.