In the generations before Noach (Bereishis 5), the verses conclude with, "and he died." Why, in our chapter, do they say only "he fathered sons and daughters"?
Hadar Zekenim: Before Noach, people did not leave righteous children, and their descendants perished in the Mabul, 1 so it is properly called death.
Moshav Zekenim: Before Noach, people knew of their fathers' death. After the Dispersion, 2 almost all knew only from second-hand accounts, which is invalid for testimony. (It is as if the death was not known.)
R. Avigdor Miller: Before the Mabul, people were living about 900 years. It was a great Chidush when someone died!