Considering there is plenty of evidence for humans being in the Americas 20,000 years ago, that means archaeological goldmines could be on the current seafloor on the eastern, Atlantic seaboard.

This is from the USGS

The ancient coastline used to be a few hundred miles out from the current coastline. When you combine that with how people tend to live near the ocean, that means that:

• Evidence for ancient civilisations could be on the seafloor
• Atlantis could even have been there

As an example of the evidence for this, fishermen have hauled up mastodon bones up to 180 miles from the current coastline.