The interaction of the nanosecond laser (FWHM = 30 ns, lambda = 355 nm) and monocrystalline silicon is investigated in air and water. Conventional optical and scanning electron microscopes are used to characterize surface ablation of the monocrystalline silicon. A numerical model is used to ascertain the time of the bubble motion in water. Morphological features of the laser-induced crater are different under various environments and frequencies. More debris is found when using high frequency ablation, and a larger zone is affected by heat when using low frequency ablation in air. There is no debris found in water, and the morphology of craters is better in low frequency ablation than that in high frequency ablation because bubbles generated by high frequency ablation affect laser transmission. (C) 2014 Elsevier B.V. All rights reserved.