When Benjamin (Robert De Niro) emerges from the rapids and seeks shelter in a nearby cave, the survival techniques he uses are all authentic. He urinates on his leg wound to disinfect it as urine contains salts and ammonia. He later uses a medicinal herb poultice under a bandage to facilitate the safe healing of the wound. He sanitized water by boiling it, then makes pine tea to further warm his body core to prevent hypothermia setting in. The fire pit he digs is taught in military special forces, who adopted it from the Native Americans. Commonly known as a "Dakota" fire pit. It is two chambers dug into the ground roughly elbow deep that join at the bottom in a "V", with the excavated dirt mounded at the rims. The larger chamber contains the fire, while the narrower one provides airflow at the base. The value of the fire pit is that it conceals firelight, as well as has the ability to be instantly extinguished and concealed by pushing the excavated dirt back in. This makes it very valuable to a soldier for escape and evasion. The knife used in the film is a Gerber LHR combat knife. Now discontinued and a collectible.
The book that Robert De Niro is seen reading at the start of the movie is "For Whom the Bell Tolls" by Ernest Hemingway. The Hemingway novel features a main character named "Robert", and deals with the Spanish Civil War, the Bosnian/Serbian civil war is the background to the movie.