Abstract: The relief of large coastal accumulative bodies, including cuspate spits, is an important subject in scientific and applied research. A characteristic feature of similar accumulative bodies is a shallow underwater part. The aim of this work is to study the shallow-island part structure of the Dolgaya Spit (the Sea of Azov) and to identify the natural mechanism that determines both the variability of accumulative body over short time intervals and the high stability of the geosystem as a whole. Digital elevation models (DEM) for the studied area were built on the basis of remote sensing data (Sentinel-2). It is established that the length of the shallow-island part is about 20 km. There are shelly shoals and islands with a complex configuration and relief. Sea level, the wind-wave regimes and the sediment load are the main factors that determine the dynamic equilibrium of the shallow-island part of the Dolgaya Spit and its relief. The Dolgaya Spit has distinctive features of a free accumulative body influenced by longshore sediment flow. The configuration of its surface part is characteristic of many cuspate spits formed by two sediment streams. But the shallow-island part develops under the influence of alternating transverse movements of water masses and waves from opposite sectors. The coexistence of signs of the near-shore bar and cuspate spit provides grounds for classifying the Dolgaya Spit not as a cuspate accumulative body (in particular as Azov-type spit) but as a separate type developing under joint action of transverse and longshore sediment flows.