Multibeam swath bathymetry data were collected with a hull-mounted Kongsberg EM120 and EM710 echosounder during RRS James Cook cruise JC035 (Chief Scientist Veerle Huvenne) in June 2009. The cruise was conducted to map Whittard Canyon, a deep ocean canyon in the Bay of Biscay. The data were edited using Caris HIPS software by Catherine Wardell and gridded at 50 m spacing (EM120) and 10 m (EM710) in a WGS84 UTM Zone 29N projection. The vertical datum of the data is matched to mean sea level (MSL). They were exported as longitude-latitude-depth triples. Funding was provided by the UK's Natural Environment Research Council (NERC) to MAREMAP, Oceans2025, and HERMIONE project (Grant no 226354).