A method of plugging at least one undesired opening in a fluid vessel can include introducing one or more plugging devices into the vessel, conveying the plugging devices by flow to the opening, and blocking the flow through the opening with the plugging devices. A system for plugging at least one undesired opening in a fluid vessel can include a deployment apparatus configured to introduce one or more plugging devices into the vessel, a sensor that measures a physical parameter indicative of leakage from the vessel, and a controller that activates an actuator of the deployment apparatus in response to receipt from the sensor of an indication of leakage from the vessel.