A sub sea actuator including an actuator housing. An activating element is movably arranged between activating and deactivating positions, respectively. A return spring is supported in the actuator housing to move the activating element into the deactivating position. The sub sea actuator includes an SMA element supported in the actuator housing and arranged with a temperature elevator configured to control a temperature of the SMA element. The SMA element acts on the activating element to move the activating element into the activating position against the force of the return spring in result of a rise in the temperature of the SMA element.