Less than 50% of the Channel Islands National Marine Sanctuary seafloor has been mapped using multibeam echosounders to produce habitat characterizations at a map resolution suitable for resource management. This is important because deep-sea coral and sponge communities are known to occur within the Sanctuary. Mapping activities and benthic survey operations were conducted aboard NOAA ship Bell M. Shimada with Beagle ROV between March 13 and March 22, 2015 in order to address these data gaps. A total of 82 square miles were mapped using the ships ME70 multibeam system. A total of 36 water samples were collected to 545 meters depth for evaluation of carbonate chemistry. The research team completed 13 ROV dives between 50 and 300 meters depth. Samples of deep-water sea fan colonies and stony coral aggregations were collected and retrieved for species identification, age, and growth studies. An extensive coral garden consisting of large sea fans with many rockfish was discovered at 60-80 m depth on the north side of Santa Rosa Island, outside of existing no-take areas.