Carry a PLB on my person inshore and offshore.
I carry a PLB. The Inreach has been used for many rescues. The PLB for many more. PLB's have a power out of 5 watts and speak to a satellite cluster that is huge and growing. The cluster uses lower earth orbit, medium earth orbit, and most recently the SAR package has been put aboard some geo sync birds at very high altitude. The PLB has a guaranteed battery life (by spec) assuming you keep it updated per the vendor spec. The PLB has a low power homing beacon receivable by all aircraft (mandated by law). USCG helos have specialize antenna to home in on that frequency for close in direction finding. When you pull the trigger the USAF, USCG, or some other international military gets a direct notification. Inreach/Iridium goes to a corporate entity that then notifies Federal officials, could result in a slight delay. In the end the rescue organization will likely be via USCG resources if you are in the water.
Interesting test I experienced: My PLB was stolen out of a rental car in Hawaii, Kauai. About a week later the USCG called and asked if I was ok. I was sitting in my kitchen in Ca. They had the position narrowed to two homes in Kauai. The signal disappeared within a few minutes. Six months later the USAF called me to check on my well being. Again the beacon had been turned on and these calls were made within minutes of their receipt of the signal. Again seemingly between two homes. For reasons I don't understand the Kauai Police refused to go to the homes on both occasions, stating something about the inability to get a search warrant based on the position not being definitive as to which property it was on. The police were also notified by the Fed. agencies. But at least it worked well and the calls were immediate.