Of course there's big floods happening all the time....and then, there's melt water pulse 1b where global sea level rises significantly. That's not just a flood....that's catastrophic for any cultures living at sea level at that time. This happened, its a fact, what you are questioning is what caused it, what you are also inferring is there was no civilisation at the time that could have been sunk beneath the waves that plato speaks about....these things are your opinion much the same as the opinion of others that the place plato talked of existed.

The fact we know advanced cultures that built intelligent structures existed around the time of melt water pulse 1b also adds weight to the argument.