In the IODP 372A proposal, working hypotheses used with respect to actively deforming gas hydrate‐bearing landslides were based on an initial calculation considering gas hydrate to occur in fresh water. This initial inaccuracy leads to predict the base of methane hydrate stability zone (MHSZ) to be at around 162 meters below the seafloor (mbsf) at site U1517 while it is expected to be between 85 and 128 mbsf. It is most interesting that important negative chloride anomalies were measured well below the theoretical MHSZ without direct evidence of the presence of gas hydrate. These anomalies are usually a strong indication of gas hydrate occurrence. This initial inaccurate hypothesis provides the opportunity to evaluate the effectiveness of the indirect salinity detection method to quantify gas hydrate.