if the story of adam and eve were true- that would mean there children would have had sexual relation-incest. i've read christians say that was not an issue at the time because of this and that- the bible doesn't give all the details of creation
on the face of it the story of noah's ark doesn't seem plausible.
but that is why a lot of people have a hard time believing the bible- totally understandable-
parting of the read sea david and goliath the story of sampson the battle of jericho the virgin birth turning water into wine walking on water raising people from the dead jesus dying on the cross for or sins heaven hell and on and on
it does sound like a fairytale to me also- and totally not provable.