Yalung's Teeth is a cave at X:348 Y:404, along the western shores of a river in southern Kyrat.
A Recurve Bow can be found here at any time after the Black Water Dragon Fashion Week quest has been started. (The quest is started from nearby Kyra Tea Weigh Station.) Though the body of the bow's owner is here before this, neither the bow nor the pond's Demon Fish will be present.
The bow is found at the bottom of the pond in the cave, next to its owner. (This is perhaps the unnamed man who, according to a nearby journal entry, had taken refuge there and was sustaining himself by eating the flesh of the Demon Fish that live in the underground pool.) At the part of the pool nearest the cave entrance are two broken wooden planks that apparently collapsed, dropping the man in to the water and drowning him. Dive down to the bottom and find the bow next to the man, being careful of the nearby Demon Fish.
A good supply of arrows (three bundles) can also be found nearby.