They probably died due to a large rain (flood) and their bodies washed down into a common chokepoint on the river, the bodies decayed and ended up on some riverbottom.
A possibility to be sure. Would 40 day and 40 nights do it? Could it be they succumbed to the same nastiness as THESE GUYS?
36 posted on 09/06/2012 9:51:22 PM PDT by ForGod'sSake
(You have only two choices: SUBMIT or RESIST with everything you've got!!!)