I was in Bolivia only once in 1986, when I crossed the border with Walter in Curumba, Pantanal, Brazil, to drink a Coke in Puerto Aguirre. It was on the other side of the Paraguaya river. The official border was between the border posts, the illegal outside of the border posts. The border guards did not bother much about who went through where. It was only astonishing for them that we wanted a stamp, they had to move for it from their hammocks. We wanted however absolutely the stamp, since there were already rumors at that tourists without stamp, because it is easier to enter outside the border posts, with lack of money of the border officials, high penalties for illegal immigration had to pay. That was too risky for us on a one-day trip.
In the adjacent city then a Cola drunk, which cost 2 million Peso, so an expensive Cola had I never.
On the river Paraguay we drove once boat, many Piranhas and water snake and otherwise Getier (big catfish, tremor eels and - rays etc.). Walter was really scared, especially when we were shaking the boat.