Shag, Arch, Blossom and Harding are the littler siblings of Alcatraz, named rocks in the San Francisco Bay that experienced “bar pilots” know to steer around. They were originally larger knobs of rock, blasted down in size to accomodate 19th century vessels, but remain menacing to modern container ships. Other characteristics of the floor of the bay can be seen in the new 3-D maps created by the US Geological Survey. “Multibeam mapping” with sound pulses was used to reveal the bottom of the bay. The maps and a report on the transformation of the underwater surfaces are available online.