This data set was acquired with a SeaBeam Instruments model 2112 multibeam sonar system during Nathaniel B. Palmer expedition NBP9904 conducted in 1999 (Chief Scientist: Dr. Gary Klinkhammer). These data files include Swath Bathymetry, Acoustic Backscatter data and were processed at sea using the open source MB-System multibeam sonar processing software. Data were acquired as part of the project(s): Multibeam Sea Test; Heat and Chemical Exchange During the Early Stages of Back-Arc Rifting in a Polar Region: Hydrothermal Activity in Bransfield Strait, Antarctica, and funding was provided by the U.S. National Science Foundation.