The extensive exploration and development of shallow water oil fields on the continental shelf require the search for new sources of hydrocarbon reserves and movement towards the deep-water or Arctic areas. Today, the development of technologies enables oil production in complex conditions of the Arctic and deep-water shelf. Such production, however, is associated with high technological and environmental risks, which necessitates the development of innovative technologies and means to mitigate environmental risks. One of the solutions is the application of underwater oil storage facilities that have gained popularity abroad. The article provides an analysis of the existing designs of underwater tanks. The main factors affecting the selection of appropriate mass and dimensional parameters for underwater storage facilities are listed, including operational conditions, stability and strength, the technology of tank and membrane manufacturing, transportation and installation on the seabed, safety and environmental requirements, and economic factors. The calculations of mass and overall dimensions of the considered structures help to determine preferable capacities and evaluate the impact of flexible membranes on the mass and dimensional characteristics of oil storage tanks. Studies have shown that using membranes reduces the wall thickness, overall dimensions, and mass of the structure. The main factors contributing to accidents during the operation of subsea oil storage facilities have been identified, along with safety barriers aimed to mitigate the negative impact on the flora and fauna of the surrounding water area. Further investigation of the issue of wax deposition in underwater tanks that occurs when the temperature of crude oil drops due to heat loss in the surrounding seawater is planned. The deposited wax can either remain in the crude oil or settle as a layer adhering to the internal walls of the tank.