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 ; 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 is thus blocked by the end stop , or only a rotation to the next dead point 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 ; 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 is thus blocked by the end stop , or only a rotation to the next dead point 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 ; 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 is thus blocked by the end stop , or only a rotation to the next dead point is possible, so that a rotation of the crank is necessary for a force conversion into the non-blocked direction. <EOS>