Seismic study of transition zones in Arctic regions in summer is troublesome because of the presence of large areas covered by shallow waters like bays, lakes, rivers, their estuaries and so on. The winter is more convenient and essentially facilitates logistic operations and implementation of seismic acquisition. But in winter there is a complicating factor - intensive seismic noise generated for acquisitions installed on the ice covering shallow waters. It is well-known that this noise is connected with flexural waves generated in ice by seismic sources. These waves are one of the strongest known coherent noises. At the same time they are much slower than surface waves well known for onshore acquisition and seem to be easy avoided by f-k filtration. However, this type of filtration fails to suppress such noise. To understand the matter the representative series of numerical experiments are conducted and prove that the main impact to noise is multiple conversions of flexural waves to the body ones and vice versa. Ways to reduce this noise are proposed and discussed.