boat horseshoe lifebuoy / inflatable
Fixed to your pulpit or your console, the buoy will be always be within reach so you can throw it to a crew member if they fall overboard. Pick up the buoy, throw it. When it comes into contact with the water, the casing opens and the buoy inflates. The ballasted case sinks and becomes a floating anchor, so that the buoy remains close to the place where you launched it.