This paper presents an experimental investigation into the flow rate of natural gas released underwater from a pipe orifice and the associated combustion behavior on the water surface in an aerodynamic channel. A stainless-steel pipeline with a diameter of 25 mm was placed in a water tank of 1 m (height) x0.5 m (width);: 0.5 m (length). Methane gas was released from a cylinder controlled by a flow meter and pressure gauge. Ten k-type thermocouples, fixed in two directions, were used to measure the temperature profile. The variation parameters of orifice diameter (1 mm, 3 mm, 5 mm), pressure range (0.02 to 0.55 MPa) and gas release depth (0.4 m, 0.6 m, and 0.8 m) were varied to study the flame geometry and temperature profile. A digital CCD camera and an infrared camera are employed to record the visible and temperature distribution, respectively. Results show that flame temperature decreases vertically; an initially high temperature region in the core flame quickly decreases in the plume region. Flame oscillation behavior is due to gas diffusion and flame turbulence. The stability of a burning flame is dependent on an increase in leakage pressure and large orifice diameter; shallow water depths provide greater flame stability. A new correlation is proposed to characterize the flame height to diameter ratio and the dimensionless heat release rate Q*. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.