Hw help please...its due tomorrow and well yeah help please!?

OK, so i have an essay due tomorrow and i need to compare and contrast floods. the floods that i will need to compare have to be the Hebrews, Noah's ark, Mesopotamian and the Aztecs.. i am having trouble coming up wit a thesis and i don't know how am i supposed to compare all of them if they don't have nothing in common wit each other.. help please and thank you :D