Direct measurements of the interfacial behavior of submerged high speed gas jets with speeds ranging from subsonic to supersonic Mach numbers were performed using high speed digital photography and shadowgraphs. The results indicate that the jets preferentially pinch-off near the axial position which in previous experimental work has been shown to correspond to the location of the maximum streamwise velocity turbulence fluctuations. Using the optical method presented in this paper, the data indicates that the electroresistivity probe technique used by past researchers to quantify the jet penetration into the ambient fluid biases the measurement by up to 30 diameters as the probe cannot identify true jet continuity as opposed to advecting bubbles. We introduce a theoretical jet penetration distance based on a simple force balance of the jet cross-section which compares reasonably well with the measured data. This theoretical jet penetration distance scales with the square of the Froude number and requires an estimation of the jet centerline properties as they evolve downstream of the orifice to accurately predict the pinch-off point. An experimental jet penetration distance is introduced and is defined as the 98.5% contour of the orifice attached gas jet presence over the measurement time.

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