James Cook cruise 035 was aimed at the detailed mapping of the Whittard Canyon system along the Celtic Margin (NE Atlantic). In 12 days, >700 km of track-lines were surveyed with the Towed Ocean Bottom Instrument (TOBI, carrying a 30 kHz sidescan sonar system with phase bathymetry capability, an 8 kHz chirp profiler and a magnetometer) and 6130 km2 of shipborne multibeam data was acquired over the 4 main branches of the canyon. This comprehensive and highly detailed dataset will provide new insights in canyon morphology, formation, sediment transport processes and into the resulting spatial distribution of benthic habitats. In addition, the data formed an indispensable base map for the planning of ROV dives during the follow-on cruise JC036.<br/