Dan
Contributor
Based on the following article, I would only get an AIS MOB that also supports DSC signalling. The Nautilus Marine Rescue GPS is probably the best package for us divers, due to the clam shell design, depth rating and size. Very interesting to see what happens on the boat side in terms of receiving the AIS or DSC signals/alerts: Testing AIS MOB beacons, ACR's DSC feature especially - Panbo
That's the reason I get the Nautilus Marine Rescue GPS (MRG) and PLB1. You have 3 different distress alert signal, DSC, AIS & 406 MHz to launch. You can delay launching the 406 MHz until you don't see any boat on the horizon. Some smaller & old boats don't have AIS, but might have DSC.
I haven't seen any PLB nor PAB (Personal AIS Beacon or what they also call it AIS MOB beacon) that is designed for diver, except for MRG which is waterproof down to 425' (130m), small enough to fit in my BCD and have DIY replaceable batteries (two of 3 volt Lithium CR123A) and float. It's time for ACR or Ocean Signal or any other PLB maker to make similar clamshell design PLB for diver.
Another reason for having MRG for me is, I've been to several overseas liveaboards that loan MRG to their guest divers for quick rescue in case of getting lost at sea, especially in the countries with questionable SAR, such as Galapagos Master, Palau Aggressor II, Maldives Aggressor II, Argo (Cocos), Spoilsport (GBR), Nautilus Undersea (Socorro). That shows the practicality of having PAB on every divers for speedy rescue.
My next trip in September will be with Blue Manta to Ring of Fire, Banda Sea, Indonesia. They don't have PAB to loan to their guest divers, but they have AIS in the boat. So, I'll bring my MRG & PLB1 for that trip.
The next trip after that I will be in Raja Ampat, Indonesia in January 2020. Fortunately they have ENOS to loan to their guest divers. I might leave my MRG at home and just bring my PLB1 for that trip.