Shock wave generation from laser-produced plasma in water confinement regime for an incident 25–30 ns / 40 J / λ = 1.064 µm laser beam has been studied. Transmitivity measurement of the parasitic plasma breakdown at the surface of water confinement has been performed with a continuous laser probe. Above 6 GW/cm2 incident laser intensity, the critical electronic density for the laser wavelength is achieved inside the plasma by cascade ionization during the pulse duration. Above 10 GW/cm2, peak power density transmitted through the plasma saturates. The laser pulse transmitted through the breakdown plasma corresponds to the part of incident laser pulse preceding the transmission cut-off.