Sea of Japan
I went looking for bathymetric data for Sea of Japan and found one stunning image at http://www.epcc.ed.ac.uk/csep/gif_figures/omf9.gif --which clearly indicates the onetime land bridges and the existence of an inland sea in paleoclimates with lower sea levels:
I also found one for the Yellow Sea, at http://www-ccar.colorado.edu/~kantha/Altimetry/Plots/yes.bath.gif (the page also has a good characterization of physical conditions):
And another for Sea of Japan at http://www-ccar.colorado.edu/~kantha/Altimetry/Plots/soj.bath.gif: