Thanks to Kurt for the tip!
NGDC has just put out a beta version of their new data viewer. It can be found here: http://www.ngdc.noaa.gov/maps/bathymetry/
Very cool! You can zoom in, and browsing through the multibeam files is really easy. It looks like the surveys are split up into sections, though, so if you need bathymetry from a certain area, you might have to do some picking apart.