Impact by a box-like structure onto shallow water is analysed with the help of asymptotic methods. The analysis is based on both the asymptotic approach by Korobkin , which was derived originally for blunt-body impact, and the experimental results by Bukreev . The flow region is divided into six parts: the region beneath the entering body, the region close to the bottom edge, the region of inertial flow of the liquid, the jet root, the splash jet and outer region. The flows inside each of the subdomains have their own peculiarities and are analysed separately. The matching conditions make it possible to obtain a uniformly valid asymptotic solution of the impact problem. The main attention is paid to the flow patterns and pressure distributions. It was found that the pressure inside the jet root can be comparable with the pressure beneath the entering body and can even exceed it. The effects of the shape of the body bottom and of the body flexibility on the liquid flow and the pressure distribution are investigated.