So one day, God, in his infinite wisdom and mercy, got pissed off at basically everyone. I mean everyone.
Except for this one guy, Noah. And Noah’s family and their families. And all but two of each different kind of animal. God told Noah that he was planning to flood the entire planet and drown, well, everyone. He further instructed Noah to build an ark of the dimensions 300 cubits by 50 cubits by 30 cubits, to carry those whom God, in his infinite mercy, had deemed worthy of salvation.
Admittedly, no one’s quite sure exactly how big a cubit is – it’s based on the length of one’s forearm, but of course, no two forearms are exactly the same size either. What is fairly certain is that there’s no way that any such creation could be large enough to fit two of every animal, even allowing for excluding fish.