I have nothing further to add myself, since I've commented in previous threads on this subject, but let me link you to a few relevant older discussions. (I've commented in the first and third ones: take that as a recommendation or a warning as you see fit!)

• Is there a generally accepted explanation among historians for the world-wide presence and prevalence of flood and nephilim stories?
• How much, if any, evidence is there of a great prehistoric flood?
• It's a common theme in fiction, but are there any actual instances of ideas or legends that are consistent across distant cultures?
• Why does so many cultures have a Great Flood myth? Did a flood really occur or is it a mythological archetype?