One of the main objectives of the REM 2040 and ETAL 2040 cruises is to investigate the possibilities of calibrating multibeam echosounders. The 1st cruises made aboard RV Thalia in 2013 and in June 2014 enabled EM 2040 data to be acquired on baseline zones with various acquisition parameters. The ETAL 2040 cruise made it possible to continue this EM 2040 calibration phase thanks to: new EM 2040 acquisitions on baseline zones, in the bay of Brest and towards Pierres Noires; EK 60 - 200 kHz acquisitions along with those of the EM 2040 - This echosounder, calibrated in basin, was fitted on beam pole, at a 45° angle. The acquired data could be compared to those from the EM 2040 (water column and reflectivity data, at the same angle and at 200 kHz frequency); acquisitions with a DYNECO video system (to be confirmed) + Shipeck grabs to make field data available. This falls under the Underwater acoustics project.