[huldah1776]

were they not drowned in the flood?

[El Cid]

They were good swimmers.

[RoosterRedux]

were they not drowned in the flood?

Apparent, depending you who you listen to, the bloodline continued after the Flood.

Was the gene in one or more of the wives of Noah's sons or did someone stow away on the ark? Who knows.

But, after the Flood, God did have the Israelites wipe out entire tribes of giants/Rephaim (every man, woman, child, and beast) of the Hittites, Amorites, Canaanites, Perizzites, Hivites and Jebusites, etc (Deuteronomy 20:16-18).

So the cleansing continued.