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The gas-dynamic expansion stage of the plasma at the air-water interface is studied numerically for the setup corresponding to the laser shock processing of materials in the water-confined regime. The plasma is induced by a laser radiation of the intensity range 4–17 GW/cm2 at the 1.06 and 0.353 μm laser wavelength. A mathematical description of the plasma is performed in the frame of transient two-dimensional radiative gas dynamics, which incorporates the system of gas-dynamic equations and the radiation transfer equation. The studies performed indicate that the plasma evolution significantly depends on the laser wavelength. For the IR laser effect the expansion mechanism is the fast propagation of the ionization wave toward the laser source, and for the UV laser effect the laser supported detonation wave is formed. The plasma radiation contributes significantly to the redistribution of energy inside the plasma domain and, for the UV effect, forms the domain of preionization ahead of the shock wave. In both cases the plasma becomes opaque: for the IR effect it occurs over a very short period of time, 3–5 ns, while for the UV effect the process takes much longer. When the laser intensity is increased, the peak intensity and the duration of the transmitted pulse tend to reach a saturation level. © 2001 American Institute of Physics.