Even when there is a legitimate mayday and there is decent radio communication and the boater has a GPS it is amazing how long it often takes the CG to establish exactly where the situation is and what needs to be done, so nobody should count on an instant response no matter what gear
you have onboard. I have been involved in several mayday calls as an intermediary with the CG on the radio and people in a panic often forget to push the talk button or let go at the critical moment or read off the coordinates incorrectly or garble their words or the signal fades or they state an incorrect location (very common) or you get the idea. I was near a boat taking on water
last summer--close enough so I was monitoring the back and forth on the radio and trying to play along with the CG to figure out where this person was exactly, and it took at least 20 minutes of back and forth and nonsense before it was determined where the boater was, and then somebody from Sea Tow or BoatUS was finally able to go there. In fact, it took a few minutes of the CG yelling at everybody before all the fishing
boats etc. stopped yakking away loudly on channel 16 on full power so we could hear what the problem boat was saying. Another thing you will find is that the private towing companies fight each other tooth and nail on the airwaves trying to get the tow, in some cases deliberately stomping on the other's transmissions to block them reaching the boater. I have heard a boater call for help and then the towing companies jumped in when the person was calling a different company. Unless the person claims the boat is going down NOW! the CG usually hands off to the towing companies, and even when the boat is going down if a tow is closer they will often beat the CG to the scene.
In any case, my main point being that even if you are on the scene trying to assist it is not all that clear cut exactly where the boat is, what is happening, who is closest, what they need, etc. I'm hoping this is not a real missing vessel lost
because of this confusion.
Now, I'm sure DSC could be a help, but the one problem with that route
is that a lot of boats still don't have it and won't pick up the alert, and I think more than 50% of boats with DSC aren't hooked up to a GPS or registered. In a real sinking emergency
I think you should hit the red button on the DSC but also go on 16 in the open and start calling MayDay, but hopefully that wouldn't confuse things.