Deception Island is the largest volcano in Bransfield Strait, a marginal basin situated behind the extinct South Shetland Islands arc.  The surface of Deception Island has been well studied but its submerged flanks have not.  A multibeam bathymetry survey was conducted around Deception Island during the TOMODEC seismic project in 2005. The seafloor morphology is dominated by extensional faults and volcanic and sedimentary features.  The northern end of Deception Island is transected by the bounding fault of the Central Bransfield Basin, the volcano’s eastern flank is characterized by slump deposits, normal fault scarps, seamounts and volcanic ridges, and the main features of the western flank are two extensional basins, separated by a ridge connecting Deception Island to Sail Rock, an andesitic seamount.  There is a strong correspondence between extensional faulting and volcanism across the island.  Data from the flooded interior do not require recent resurgence of the caldera floor.