Flares are legally required and are useful in some situations. However, don't assume that they will be seen or, if seen, acted upon. Many boaters are clueless and will just assume someone's shooting off fireworks.
I have personally seen one situation which made me very distrustful of flares...even very bright ones.
One dark night a Mayday was broadcast by two older gentlemen who had run their sailboat aground when entering the Rappahannoc River in the Chesapeake Bay. They were in 4' of water, the wind was blowing 15 knots or so, it was cold, and they were very scared. They had a handheld VHF
and a bunch of flares.
They said they could "see the bridge", i.e., the big highway bridge over the river, but didn't have an exact location. The Coast Guard ran their 41-footer all the way from the river entrance to the bridge and back again. Several times. They also overflew the area with a chopper. A commercial towing service also did the same track. Nothing. The old guys shot off several flares. Coast Guard didn't see anything.
Finally, the Coast Guard said, "OK, we're gonna shoot off a flare which will light up the whole East Coast. Tell us when you see it." They did. The old guys saw nothing. Clear night. Distances were small. Yet no one saw anything.
Coast Guard began to think this was a hoax. I was anchored in a neighboring river just to the south, and had heard the whole thing. I told the Coast Guard I could hear the guys clearly, and they sounded scared.
After almost 3 hours of searching, a Navy SAR team in a chopper from the Norfolk area found them....they had run aground on a prominent sandbar on the north side of the river, about halfway between the river's entrance and the bridge. Just where you'd expect them to be. Yet, no one saw them for upwards of 3 hours, despite having considerable resources on site.
Moral: flares are good, but don't assume they'll save your bacon. Handheld VHF
's are mandatory. Keep them charged and, if possible, have extra batteries. And, in these days and times, have a working battery-powered GPS
so you can report your exact position. By the way, some new handheld VHF
's have built-in GPS