Plasma, recognized as the fourth state of matter, exhibits unique properties that make it highly suitable for laboratory investigations and technological applications. In this study, key plasma parameters, including expansion velocity, temperature, and density, were experimentally measured using shadowgraphy. The experiments were conducted with a Nd:YAG laser at pulse energies of 140 and 200 mJ in two different environments: air and water. Plasma formation was induced with a fundamental wavelength of 1064 nm, while shadowgraphy employed the second harmonic at 532 nm. Temporal imaging over 1–10 μs intervals allowed detailed analysis of plasma front propagation. The results indicate an average plasma expansion velocity of 3.54 km/s in air and 2.74 km/s in water. The plasma temperature was measured at 3435 K in air and 2008 K in water, while the density values for 140 and 200 mJ pulses were 5.04 and 5.35 kg/m³ in air, and 4.91 and 4.95 kg/m³ in water, respectively. Temporal evolution of these parameters revealed a gradual decrease in temperature, velocity, and density after plasma formation. This study demonstrates that shadowgraphy provides an effective tool for precise plasma diagnostics and comparative analysis across different environments. Moreover, the high sensitivity and dynamic characteristics of laser-induced plasma offer potential applications in optical cryptography and sensitive environmental monitoring, where spatial and temporal plasma patterns can function as secure data channels or environmental indicators, responsive to subtle changes in the surrounding medium. These findings may contribute to the development of advanced laser-based systems for information encoding and environmental surveillance.