The underwater release of air from the sudden rupture of a finite canister was studied by time-resolved pressure and interfacial geometry measurements. Two distinct dynamical regimes for the air were identified: an inertial regime, in which the air oscillated with increasing frequency, and a capillary pinch-off regime, in which emerging air bubbles pinched off from the air remaining in the canister. The temporal scales for these regimes were identified, and the inertial regime was shown to follow Rayleigh–Plesset dynamics, and was characterized by an empirically defined length scale associated with the air volume. The behavior of the two regimes in frequency-space was modeled by a modified Rayleigh–Plesset equation accounting for volume losses, turbulent damping, and a time-dependent capillary forcing.