the ones who were not eaten while bobbing on the surface, who didn't succumb to hypothermia or who would not have already died from something else
90 percent
By Accident
Because prepositions can often by exchanged for one another (in this case the prepositions are "by" and or"), either way is grammatically correct in this sentence. I tripped on accident or I tripped...
If you mean something happened that was not intentional, it should be by accident. "The boy stepped on the cat's tail by accident."