Most archaeologists reject the idea of an ancient advanced civilisation and a cataclysmic event which destroyed it. Myths, bible and vedic stories are considered not sufficient and thought to be inventions. They therefore consider the evidence left by that civilisation to be creations made by the civilisations we know of, Egyptians, Incas or others. They therefore have to claim that these civilisations could produce the artefacts that exist with the copper or bronze tools that they had. See Evidence of rock cutting for why this is a ludicrous claim that cannot be true.
Since the last glacial maximum roughly 20,000 BP, sea level has risen some 200 to 300 feet. A lot of the evidence of this civilisation will be below sea level, but there is sufficient above sea level. The evidence that is below sea level is important to give us a date. These constructions must have been made before sea level rose to its current height.
However those who do comment on the possibility of advanced ancient civilisations capable of hard rock machining, such as Graham Hancock and Chris Dunn, duck the issue of how it could have happened. We know in pretty fine detail the story of human development. Widespread agriculture did not develop until the neolithic and there is evidence in ice cores that large scale development of metallurgy did not happen in the hundred thousand years before our industrial revolution. The emissions that this caused are easily detectable in ice cores.
If you believe that metal machines were necessary to create the evidence of rock machining that we find around the world there are some inevitable conclusions. Though they may be hard to accept. The necessary metal was either created on earth in small-scale processes that did not emit the pollution we have found it necessary to emit. Or it was brought to earth from somewhere else. Both require science considerably beyond our current science.
The most economical explanation is that there was a relatively small group of people possessing advanced science and able to travel the world. And that these people kept themselves separate from mankind except for a few favoured groups. They would have been seen by those who came into contact with them in pretty much the same way as the cargo cult islanders viewed the Europeans who visited their islands in ships and planes.
And the most economical explanation of where these people could have developed the necessary advanced science without polluting earth, or leaving other evidence of sufficient mineral extraction, is that they visited earth from another planet.
If that was the case they must have been able to thrive on this planet. We have evidence that DNA-based life forms can evolve technologically capable beings. And that the various varieties of these are sufficiently similar to be able to interbreed. We know of Homo Habilus, Erectus, Naledi, Floriensis, Denisova, Neanderthal and of course Sapiens. It is not too far a stretch of the imagination to imagine that DNA-based lifeforms developing on another planet similar to earth might produce a being pretty similar to Homo Sapiens.
The next bit of this logical sequence of deductions is to work out how recently they were here and when and why they left, died out or merged with our current population. We can also ask when they might have communicated to mankind the symbols of the god’s power that are now being rediscovered as we find out about ball lightning.