In this contribution we report on modeling underwater explosion in the framework of molecular dynamics. We have developed a computer program which allows studying the underwater explosion in two dimensional Lennard - Jones liquid. For studying the structure of shock waves, a special technique was developed. It allowed observing the form of a shock wave and estimating its velocity. The most striking result of the investigation is that the shape of a shock wave is changing with time as if the shock wave disintegrated into two parts. The phenomenon is analyzed similar to the approach accepted for solitons. An equation for two-dimensional shock waves which generalizes the Korteweg-de Vries equation for a one-dimensional medium is suggested.