Abstract: The invention relates to a submersible system (1) comprising at least a first frame structure (2) for horizontal storage of tanks (3) with a positive buoyancy in water therein, wherein the first frame structure (1) has a negative buoyancy in water and comprises at least two storage positions (4) for supporting at least two tanks (3), wherein the storage positions (4) are arranged side by side in one level and each storage position comprises at least one cradle (4) for supporting a tank (3) from below, and wherein the system (1) comprises a fastening device (6,11) having a first and a second state, wherein: i. when in the first state, the fastening device (6,11) is configured to permit positioning of a tank (3) from above into the at least one cradle (4) and; ii.