GHASS 2 cruise follows the GHASS cruise, which took place in September 2015 onboard the R/V Le Pourquoi pas?. The aims of this first cruise was to study the dynamics of the free gas/gas hydrate system and the factors triggering the sedimentary deformations and submarine instabilities previously suspected on both sides of the Danube Canyon. Following this exploration cruise where gas hydrates were sampled for the first time in this sector of the Black Sea, we demonstrated that the dynamics of gas hydrates, the geomorphology and sedimentary architecture control the location of the gas emissions detected in the water column (up to 450 m in height). Seismic data analyses (HR and SYSIF) have allowed us to partly characterize the gas hydrate system and the numerical modeling of the hydrate stability zone has allowed proposing various scenarios of destabilization of the hydrates in the past, as well as predicting their future evolution. With this comprehensive view of this fluid system, GHASS 2 has focussed on the north-eastern sector of the Danube Canyon and aims to get further insights in the characterization and quantification of the free gas/gas hydrate system. The objectives are threefold: (1) characterize the whole gas system, from the source to the hydrosphere via the migration paths, (2) quantify the gas fluxes at the water/sediment interface (methane and carbon balance) and (3) constrain the temporal evolution of the gas hydrate stability zone established by the numerical modeling, from the last glacial period (-20 kyr) to the present-day and the close future. This evolution may have triggered several sedimentary instabilities discovered during GHASS. The quantitative approaches considered for this cruise are multidisciplinary (geophysical, geotechnical, sedimentological, structural, bio-geochemical, microbiological) in order to understand the processes involved in the methane cycle and gas hydrate dissociation. Seismic reflection data are constrained by direct measurements with PENFELD penetrometer (with the 50 m length version). Acoustic data of the water column and the water/sediment interface (seabed and subsurface) are now constrained by in situ observations, sampling and measurements during NAUTILE dives as well as by water sampling from CTD Rosette and coring (Calypso, interface multicorer). Flow rates of free gas was measured with the NAUTILE instrumentation (PEGAZ).