A liquid jet plunging in a pool of the same liquid may entrain air in the form of bubbles. This process has received much interest in the past due to its complexity and to its numerous applications, especially in bubble-mediated gas exchange. A study of plunging jets was undertaken focusing on low enough air entrainment rate to enable the individual tracking of every bubble. This Lagrangian point of view gives access to the bubbles' trajectories as well as their residence times, a crucial quantity for gas exchange. While individual bubble motion is essentially random (owing to turbulence), average quantities were found to be strongly correlated to experimental parameters.