Adventures at Sono RiverEdit
In 1957, Harold Oxley wrote ideograms onto a sheet of paper in the jungle camp of Soviet Special Forces in Brazil. Indiana Jones deciphered the message as "The water sleeps until the great snake" and interpreted the great snake as referring to the Amazon River. However, he had no idea what should be meant by the sleeping water. Irina Spalko ordered a map brought to her on which she found the Sono River. She explained that "sono" was the Portuguese word for "sleep".
The Soviets followed the course of the Sono River, cutting their path through the jungle. During the subsequent chase, Indiana Jones succeeded in escaping together with Harold Oxley, Marion Ravenwood, Mutt Williams, and George McHale. Marion steered the duck in which they fled off a cliff, landing it on a huge tree that was growing on the ravine's side. The tree slowly bent, and the duck was smoothly lowered in to the Sono River.
While they were floating on the water, Oxley repeated his earlier words: "Three times it drops." The duck then went over three waterfalls before ultimately landing upside down in the river. There they found a waterfall which fell down from two holes in a rock which looked like the eyes sockets in a human skull. Remembering the verse of T. S. Eliot that Oxley had used as a clue, Mutt concluded that the entrance to Akator was hidden behind the waterfall.
Behind the scenes Edit
No river of this name exists near Ilha Aramacá. There are two rivers named Rio do Sono (Sono River) in Brazil. One of them is in the state of Tocantins, about 3000 km away from Ilha Aramacá, and discharges into the Tocantins River, not into the Amazon River. The other one is in the state of Minas Gerais, still farther away, and does not discharge into the Amazon River, either.
There are videos from a waterfall of the Rio do Sono in Tocantins which are quite similar to the overview of the third waterfall shown in the movie. This waterfall, with a digital processing in order to make it appear much higher, may have been used for this overview.