I would look into a rescue streamer as discussed in the signalling section. Should you become seperated from your dive boat this will greatly enhance visibility to air units during daylight hours. for twilight or darkness a waterproof flashlight with a directed beam is a fair signalling devise. My use of the strobes only gave me a eye twitch. They are nice if your unconscious. You may elect to make for shore. The surf is actually one of the most dangerous areas of the seas, so a local knowledge of conditions is helpfull. If you make a successfull landfall, a metal match with your knife will provide reliable fire starting,neccessary for signalling and warmth. I doubt Altoid tins are rated for many atmospheres, so Id keep it simple.