The OSCAR (Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge) data set is an interdisciplinary collection of physical oceanography and geophysics measurements. Data collection took place in the Panama Basin, bounded in the north-west by the Cocos Ridge, by the Carnegie Ridge in the south and by South and Central America in the east and north, respectively. Measurements were collected during RRS James Cook cruises JC112 and JC113 (05/12/2014 to 16/01/2015), RRS James Cook cruise JC114 (22/01/2015 to 08/03/2015) and RV Sonne cruise SO328 (06/02/2015 to 06/03/2015). The project investigated the effect of the cooling of young oceanic crust close to a mid-ocean ridge. It is here that rapid cooling is dominated by hydrothermal circulation of seawater through the crust, which is then discharged into the ocean along the ridge. Once in the ocean, released heated seawater mixes with the ambient cold water to form a plume, which provides a mechanism to lift the densest waters away from the bottom boundary layer. Data were collected using Bottom Pressure Recorder, Acoustic Doppler Current Profiler (ADCP), Magnetotelluric Lander, CTD, Vertical Microstructure Profiler, Synthetic Aperture Radar, Ocean-bottom seismograph and Multibeam echosounder. Measurement of salinity, oxygen and helium were also made and zooplankton samples collected with vertical net casts. This multidisciplinary, collaborative research project was led by Professor Richard Hobbs at the Department of Earth Science, University of Durham, UK and funded by Natural Environment Research Council (NERC) grant NE/I027010/1.