Everyone who dives must carry a buoy. Some people choose to have a nice little elegant one, but that is not always convenient. You use the buoy to show yourself on the surface and the better you do that, the more effective you are. A small buoy or a black one simply reduces the chance of being seen. Choose a decent sized orange buoy, say medium. Take a spool so that you can release the buoy from depth. On board they can help you and show you how to best use the buoy.