"Repent of your sins and get on the ark. Walk through that door and be saved."
Of course Noah was called a preacher of righteousness, so who did he preach to?
2 Peter 2:5 if he did not spare the ancient world when he brought the flood on its ungodly people, but protected
Noah, a preacher of righteousness, and seven others;
The argument could be made that the flood could have still been local and that the reason Noah was ordered to build the ark instead of just leave the area was so that the people he lived with could have an opportunity to at least hear his message and repent. I'm undecided on this issue, but I've heard that there is evidence of a rather large flood in that area several thousand years ago. And when I say "large" I mean on the order of covering the entire state of Denmark. So both sides make good points.
And in relation to the 船 character, I've studied it a little bit and have an idea of how characters are formed. The meaning part of the character is 舟, which indicates a boat. The part on the right does not mean "eight" and "people." I believe, just as the part on the left is a meaning part, the part on the right is a phonetic part. But phonetic parts also influence the meanings of characters when they're first made. So it's possible that the part on the right influenced the meaning. However, the character above is the simplified version of a traditional character that looks like this: 舩. That version is closer to the original, and it does not have the 口 part (which actually means "mouth" and may refer to people or may just refer to holes or cavities). I've been told, though, by an old professor that no one really quite knows why the part on the right (that is, 公) was used. But I have a friend who wrote a paper about it. I can ask him.
Actually, it appears that the simplified 船 might've been closer to the original than the traditional character 舩. And that's true of some simplified characters. Here's the link:
字典中 船 字的解释