There is no question that the Noah account is lifted directly from earlier Sumerian and Babylonian accounts. So, if any account is truthful, it is more likely to be the original.
If we are going to simply accept the truthfullness of literature at face value, without checking to see if the events described are even possible, perhaps other pertinent questions might be:
Did Jason really sail in the Argo in search of the Golden Fleece?
Did Ulysses really have all those fabulous adventures returning from the Trojan War, including having his crew turned into swine by a goddess?
Did St. Brendan really build a boat of oxhides and sail from Ireland to various lands in the Atlantic?
Did Prince Caspian really sail to the edge of the world in the Dawn Treader?
All these events are published as actual events in the writings of various cultures, some ancient, others more recent.
Unfortunately, with regard to any alleged global deluge, there is also no question that many civilizations, such as Egypt, India, and China, were already thriving during the years which the Bible claims the flood occurred. We know the names of many of the pharoahs and kings from this time, and have many artifacts from these cultures. None of these cultures recorded any period of catastrophic flooding, or even noticed anything out of the ordinary.
Why?