MOSE consists of rows of mobile gates on the seabed at the three inlets that can be raised to temporarily seal off the lagoon from the sea during high tide. There are 78 gates grouped into four barrier rows. At the Lido inlet, the widest, there are two barrier rows of 21 and 20 gates, respectively, linked by an artificial island (the island connecting the two rows of gates at the centre of the Lido inlet also accommodates the technical buildings housing the system operating plant). In addition, there is one row of 19 gates at the Malamocco inlet and one row of 18 gates at the Chioggia inlet.
The gates consist of metal box-type structures  wide for all rows, with a length varying between  and from  thick. The gates are connected to the concrete housing structures with hinges, the technological heart of the system, which allow the gates to move while attached to the housing structures on the seafloor.
Under normal tidal conditions, the gates are full of water and rest in their housing structures. When a high tide is forecast, compressed air is introduced into the gates to empty them of water, causing them to rotate around the axis of the hinges and rise up until they emerge above the water to stop the tide from entering the lagoon. When the tide recedes, the gates are filled with water again and lowered into their housing.
The inlets are closed for an average of between four and five hours, including the time taken for the gates to be raised (about 30 minutes) and lowered (about 15 minutes).
To guarantee navigation and avoid interruption of activities in the Port of Venice, when the mobile barriers are in operation, a main lock is constructed at the Malamocco inlet to allow the transit of large ships; while at the Lido and Chioggia inlets, there are smaller locks to allow emergency vessels, fishing boats and pleasure craft to shelter and transit.
Operating procedure dictates that the gates will be raised for tides of more than  high. The authorities have established this as the optimum height with respect to current sea levels, but the gates can be operated for any level of tide. The MOSE system is flexible: depending on the winds, atmospheric pressure and level of tide, it can oppose the high water in different ways – with simultaneous closure of all three inlets in the case of exceptional tides, by closing just one inlet at a time, or by partially closing each inletgiven that the gates are independentfor medium-high tides.