The article presents the results of paleogeographic and oceanological expeditionary studies of the Dolgaya Spit of the Sea of Azov, obtained in 2021. The complex of conducted work consisted of: drilling wells, measurements of sea currents and the thermohaline structure of adjacent waters, as well as hydrochemical, hydrobiological, lithological sampling and archaeological finds. It is shown that for any wind direction near the western (Sea of Azov) coast of the Dolgaya Spit, there is a constant alongshore current. With a westerly wind, it is purely drift, with an easterly wind – compensatory. This current contributes the transportation of shell material from the Yelenina and Zhelezinskaya banks and abrasion products from the western bedrock coast. New data about the structure of well sections from different areas of the Dolgaya Spit are presented. In the lower horizons of wells drilled at the base of the spit, as well as in lagoons, water samples were taken, the total salinity in which is twice the salinity of the Sea of Azov. However, the upper water-bearing horizon of the Dolgaya Spit islands is well washed with the Sea of Azov waters. Investigations of the islands made it possible to reveal differences in their structure, composition of sediments and benthic fauna. The noted features of the stratigraphy and composition of sediments that compose the island bars, are explained by the differences in their physical and mechanical characteristics and the lithodynamic conditions for the transportation of sedimentary material. Most of the deposits of the islands are composed of shell detritus of varying degrees of fragmentation, organogenic detrital sands, and individual shell valves. The shellfish Cerastoderma dominates in the shell material of the sediments. Finds of archaeological artifacts on the insular part of the spit date back to the 2nd century BC and the 13th–14th centuries AD.