the rio grande. >> oh, my god. right there. >> reporter: at first, law enforcement believed these were desperate attempts to escape. then they began to hear radio traffic. coordinates. >> right there. oh-oh! >> in the water. >> that's a recovery team. >> just a recovery team? recovery team right there. >> reporter: the cartels even began organizing search and rescue teams and suddenly the videos made sense. drug smugglers hurling their stolen vehicles back into the rio grande were doing it for one reason. to protect their dope at all costs. >> oh, we had a splash down. a splashdown. en route. >> they don't mind losing the truck into the river. at the end of the day if they can recover 2,000 pounds of march narcotics, they're going to protect that inventory. >> it's going under. just about on the -- >> reporter: inside mexico, the army has visibly taken over much of the security any border towns. local mexican police who are not