The present paper focuses on experimental tests performed in an experimental outdoor basin with three gases (air, CO2 and methane) in order to characterize the consequences of underwater gas release. Water elevation (fountain effect) and surface velocity where measured for various mass flow. Results for maximum water elevation clearly show a strong influence of gas flow rate with an increase of water elevation with decrease of gas density. Results obtained for current velocity with air and methane release show an increase of water velocity with gas flow rate. On the contrary, for CO2 release water velocities are lower due to solubilization process of CO2 in water column involving decrease of gas momentum.