Methods of SCUBA hydrobiological surveys are discussed on the base of the author’s 18-year experience in the western Tatar Strait (Japan Sea) and in the Okhotsk Sea. Typical errors of the assessments are analyzed. So far as the methods of underwater researches develop actively, there are no universal one in this field. Regular sampling and uniform assessment methods do not guarantee to avoid the errors but usually cause excessive volume of samples and man-hours. Optimal planning of the sampling should be based on statistical analysis of preliminary information about distribution of the assessed objects in the area of survey. Planned number and location of the sections, stations and samples should be adjusted on the spot, if necessary, following the principle of sufficiency for obtaining representative data. The sections should be performed taking into account types of the coast, the stations - in accordance with natural biotic stratification. Sampling tools and methods should be chosen in dependence on nature, size, density, and distribution patterns of the assessed objects and specific conditions of survey. Modern technical means of underwater video surveillance, echolocation and satellite navigation must be involved into practice of SCUBA surveys. Some original sampling tools developed by the author are presented. Their use can significantly reduce the SCUBA man-hours, and in some cases allows to manage without diving. Rational planning and competent conducting multiply effectiveness of SCUBA survey, allowing to reduce its labor and time costs.