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The knowledge of submerged ancient civilizations is extensive, but just not wide spread. It isn't something that the powers that be wish to disseminate.
And based only on my limited observations, many or most of which were "discovered" NOT through concerted efforts by teams actually looking for them but by someone stumbling upon them. Seems that's the way it happens most of the time on land also.
It isn't something that the powers that be wish to disseminate.
Gotta wonder about that since so much of it disappears down a rabbit hole. It brings to mind the mysterious finds just off the southwest shores of Cuba some years ago. The initial and followup findings, done by the owners of an underwater surveying company, indicated geometric patterns, some very large, sitting on the sea floor almost a half mile down. There's been no followup of it since that I'm aware of.