Structure of umbelical arranged to connect a diver, in particular a CCD "Certified Commercial Diver", with a support ship and/or with a safety diving bell, said structure of umbelical comprising at least: - a duct crossed, in use, by a breathable gaseous mixture that is supplied to said diver; - a duct crossed, in use, by a breathed out flow produced by the diver during the breathing of said breathable mixture; - an electric cable through which electric energy is supplied to the diver; - a connection device arranged to connect in a removable way a first portion of said umbelical that, in use, is arranged on the side of the diving bell and/or of the support ship, and a second portion of said umbelical that, in use, is arranged on the diver's side, said first and said second portion (10a, 10b) being engaging with removable way, in order to move from a assembled configuration to a disassembled configuration, each of said first and of said second portion (10a, 10b) being equipped with a plurality of cavities, in each cavity housing, in use, a respective portion of said ducts (61,62), or of said cable; said structure of umbelical characterized in that said connection device is provided with at least one passage, or meatus, defined between a face of said first portion and a face of the second portion of said connection device in said assembled configuration, said passage, or meatus, extending up to a hole made on the outer surface of said connection device, in said meatus a first predetermined pressure P1 being present, with P1 less, or equal, to the atmospheric pressure; and in that said structure of umbelical comprises, furthermore: - a source of a gas at a second predetermined pressure P2 with P2>P1; - a valve arranged to pneumatically connect, or disconnect, said source of pressurized gas and said meatus, said valve for connecting, or disconnecting, arranged to connect said source of gas with said meatus, in order to increase the pressure that is present in it and cause, then, the separation of said first portion from said second portion of said connection device and then the movement of said connection device from said assembled configuration to said disassembled configuration. - a duct crossed, in use, by a breathable gaseous mixture that is supplied to said diver; - a duct crossed, in use, by a breathed out flow produced by the diver during the breathing of said breathable mixture; - an electric cable through which electric energy is supplied to the diver; - a connection device arranged to connect in a removable way a first portion of said umbelical that, in use, is arranged on the side of the diving bell and/or of the support ship, and a second portion of said umbelical that, in use, is arranged on the diver's side, said first and said second portion (10a, 10b) being engaging with removable way, in order to move from a assembled configuration to a disassembled configuration, each of said first and of said second portion (10a, 10b) being equipped with a plurality of cavities, in each cavity housing, in use, a respective portion of said ducts (61,62), or of said cable; - a source of a gas at a second predetermined pressure P2 with P2>P1; - a valve arranged to pneumatically connect, or disconnect, said source of pressurized gas and said meatus, said valve for connecting, or disconnecting, arranged to connect said source of gas with said meatus, in order to increase the pressure that is present in it and cause, then, the separation of said first portion from said second portion of said connection device and then the movement of said connection device from said assembled configuration to said disassembled configuration.