I should preface by saying I don't believe in a global flood as the Watchtower teaches some 4-5000 years ago and I mainly see this story allegorically. However, it's not unreasonable that a Mesopotamian flood occurred thousands of years ago that flooded all the land as far as the eye could see.
With that said, 2 Peter 2:5, in some Bibles say, "a
proclaimer of righteousness."
The Greek word means, "a herald or messenger vested with public authority, who conveyed the official messages of kings, magistrates, princes, military commanders, or who gave a public summons or demand, and performed various other duties. In the NT God's ambassador, and the herald or proclaimer of the divine word."
Within the framework of the story, could Noah simply have proclaimed to his family? Or have been a proclaimer by his actions, simply being a righteousness man in a violent world? Or been an ambassador the proclaimer by building the ark? And even being a preacher, does that mean going house to house?
The Watchtower retrofits door-to-door evangelizing, a modern invention, backwards and writes themselves into every story in the Bible.