Hmmmm.... You got me thinking there about Noah, the command given to him and his three sons entering the ark. So I researched.
Jehovah gave that command just 7 days before the deluge came.
News about the flood came to Noah before any of his sons were born. He was instructed to build that ark, while he bore sons, and saw them grow, get married and so forth. The Bible tells us that only Noah found favour with Jah. So what happened during those many years? Just because the Genesis account doesn't mention that Noah preached, what do you think Noah did when the neighbours asked him, "What the hell is that, Noah, that you are working on"?
Jesus also said that the generation before the flood, took no note. No note of what? Did Noah keep it a secret?