Seawater filtration is tested on the experimental stand with 10 types of single- and double-layer filters for water samples collected in 3 sites with different environments in the Severnaya Bay (Peter the Great Bay, Japan Sea). Quality of the filtered water is evaluated by several parameters: temperature, coloration, turbidity, transparency, odor, flavor, foaminess, and salinity. Bio-balls, haydite, ceramics, alundum, gravel, zeolite, plastic, plastic in paraffin, sulphonated coal, and sea sand were used as a filler for the single-layer filters and haydite + gravel, haydite + ceramics, sand, sulfonated gravel + sand, zeolite + plastic + sand, and plastic in paraffin - for the double-layer filters. Dependence of the filters discharge capacity on fineness of filler and filtering time is determined. An algorithm for selection of optimal filter and filler is proposed that allows to improve the filter efficiency. The double-layer filters were the most effective in the experiment. So as a long-time filtering causes plugging of the filler pores and lowering of the filtered water quality, the filters with heightened discharge capacity are more effective.