Subsea shut-off device for use in water depths of more than 30 m, for actuating a valve having a slide gate, comprising - a watertight, oil-filled housing, - a crank mechanism arranged in the housing, and - a rotary actuator; the rotary actuator being designed to actuate the slide gate of the valve via the crank mechanism, the crank mechanism having a slider-crank mechanism which has a crank, a push rod, and a joint rod having a first and a second end, the first end of the joint rod being fixed to the crank, and the second end of the joint rod being connected to the push rod via a joint, and the push rod being designed to actuate the slide gate of the valve; the crank having a first end stop and a second end stop, and a rotational movement of the crank being possible only between the first and the second end stop (26a, 26b); characterised in that the crank mechanism has a first dead point and/or a second dead point, and the first end stop is arranged close to the first dead point and/or the second end stop is arranged close to the second dead point, the first end stop and the second end stop defining a maximum rotation angle for the crank of more than 180°, so that a force on the push rod in one of the end stops (26a, 26b) is thus blocked by the end stop (26a, 26b), or only a rotation to the next dead point (27a, 27b) is possible, so that a rotation of the crank is necessary for a force conversion into the non-blocked direction. - a watertight, oil-filled housing, - a crank mechanism arranged in the housing, and - a rotary actuator; the rotary actuator being designed to actuate the slide gate of the valve via the crank mechanism, the crank mechanism having a slider-crank mechanism which has a crank, a push rod, and a joint rod having a first and a second end, the first end of the joint rod being fixed to the crank, and the second end of the joint rod being connected to the push rod via a joint, and the push rod being designed to actuate the slide gate of the valve; the crank having a first end stop and a second end stop, and a rotational movement of the crank being possible only between the first and the second end stop (26a, 26b); characterised in that the crank mechanism has a first dead point and/or a second dead point, and the first end stop is arranged close to the first dead point and/or the second end stop is arranged close to the second dead point, the first end stop and the second end stop defining a maximum rotation angle for the crank of more than 180°, so that a force on the push rod in one of the end stops (26a, 26b) is thus blocked by the end stop (26a, 26b), or only a rotation to the next dead point (27a, 27b) is possible, so that a rotation of the crank is necessary for a force conversion into the non-blocked direction. the rotary actuator being designed to actuate the slide gate of the valve via the crank mechanism, the crank mechanism having a slider-crank mechanism which has a crank, a push rod, and a joint rod having a first and a second end, the first end of the joint rod being fixed to the crank, and the second end of the joint rod being connected to the push rod via a joint, and the push rod being designed to actuate the slide gate of the valve; the crank having a first end stop and a second end stop, and a rotational movement of the crank being possible only between the first and the second end stop (26a, 26b); characterised in that the crank mechanism has a first dead point and/or a second dead point, and the first end stop is arranged close to the first dead point and/or the second end stop is arranged close to the second dead point, the first end stop and the second end stop defining a maximum rotation angle for the crank of more than 180°, so that a force on the push rod in one of the end stops (26a, 26b) is thus blocked by the end stop (26a, 26b), or only a rotation to the next dead point (27a, 27b) is possible, so that a rotation of the crank is necessary for a force conversion into the non-blocked direction.