I have ordered the raymarine system for new boat as seems to be the best option I have seen. Mind you with 10 tags is not cheap, but then neither is a life!!!!
The Lions den guy was at LIBS and the system has been teken up by Volvo for the next 3 years global challenge races I believe.
Seems to be catching on, its some kind of a hydrophone system apparently.
Seem to remember talking to SWMBO when on TV, "well that's no good then" but can't remember why, & SWMBO is in bed now, so can't find out right now. Thinking about it, I feel tired myself, so night night.
That was it.We thought the same thing!
Raymarine works with a constant signal & alarms when out of range, some 30ft, but no doubt adjustable for the big boys.
The Raymarine system requires two control units which talk to each other on large boats, so when you go out of the range of one you are handed over to the other receiver so that you don't get false MOB alarms when SWMBO goes forrard to pull in the fenders.
Its an excellent system and very easy to install and operate.
Recently I was sailing from Roscoff to Plymouth and I was thinking what would happen if I or anyone else would fall overboard and there wasn't anyone nearby to raise the alarm? Is that it? The end? Or the water behind the ferry is monitored somehow?