Imagine a tribe of nomads where all the males have the blessing of being were-stallions. The tribe would not need to have ordinary horses to move around, all mounted warriors would be female and a curious custom could be that when a couple gets married, the girl rides her chosen to the altar.
As the PCs cross a brigde/tree over a deep river they see the glimmer of gold and jewels lying at the bottom. At further inspection they notice that it is the skeleton of a man still holding on to a sack of treasure. Will the PCs try to dive to get it? What killed the man? Did he simly not let go of the bag he could not swim to the surface with? What cleansed his bones so? Are there flesh-eating beings that dwell in the deep? Can the players resist the chanse of being wealthy for once?