The people of Sodom and Gomorrah and the towns around them did immoral and unnatural things. Those people are an example of those who are punished with fire that never goes out.
The water of the flood is a picture of the way that baptism now saves you too. It doesn’t save you by washing the dirt off your body. Instead, it’s your way of promising God that you’ll keep a clear conscience by the same power that raised Jesus Christ from the dead.
Still, everyone from the time of Adam to the time of Moses was under the power of death. That even included people who didn’t sin by breaking a command from God, the way Adam did. But Adam also gives us a picture of how the Messiah could come and do something that would affect everyone.
Christ didn’t enter a sanctuary made with human hands that was only a copy of the true one. He entered heaven itself in order to appear before God on our behalf. He’s there right now.