New experiments on plunging jets have been conducted to investigate the parameters controlling the entrained gas flow rate. On a small-scale experiment (jet diameter 7.6mm, jet velocity from 1 to 10m/s, fall height up to 0.5m), we quantified the entrained gas flow rates using conical and Doppler optical probes as well as the varicose and sinuous corrugations of the jet. These data were used to test Sene's 1998 model. On one hand, Sene envisioned an entrainment mechanism equivalent to a volumetric pump: we found his proposal valid for turbulent coherent jets with an interface deformation up to 0.4 times the jet diameter. On another hand, and contrary to Sene's model, the deformation was found to be linear in velocity so that the gas flow rate increases with the jet velocity square (and not as Ui 3 ). To test further Sene's proposal, we used a larger facility (diameter 2 to 20cm, impact velocities up to 22m/s, fall height from 2 to 9.5m) that give access to more complex jet topologies including stripped jets, aerated jets… Preliminary results gathered in such conditions will be presented and discussed.