USGS
We’ve discovered thousands of previously uncharted underwater mountains, which are also known as seamounts. They are included in the most detailed map of the ocean floor ever produced.
The seamounts were compiled by a team led by David Sandwell and Brook Tozer at the Scripps Institution of Oceanography in San Diego. Their new topographical map has uncovered more than five thousand seamounts and possibly as many as ten thousand. The exact number still need to be confirmed, as they have not been counted individually yet.
source: newscientist.com