In the Coast Guard we carried penflares in our personal gear. This was before the dedicated rescue swimmer program, so there was a lot of improvising. I found them usefull to reconnect with my boat when we had multiple swimmers in the water.Remember, the projectiles and illumination stream are small . I always tried to signal riding the top of a swell and catch the wind, something of an art. My greatest success was manning the lookout tower overlooking the bar in Oregon. A small boat lost power and was drifting into the rocks. Our own MLB was within 100' surrounded by several other boats. To put it bluntly, they were skylarking the girls in the opposite direction. My handheld radio decided to die at that moment ( nobody charged the batteries) The telephone to base got a busy signal ( the cook was ordering supplies on the emergency line) I'm on the catwalk yelling my head off and waving a storm pennant. I finally reached for my flare pistol and put one ( pure luck) past the coxswain's ear. They immediately assisted the disabled boat.