Steve, I think boats often have their batteries below the floor but only just under it and certainly not in the bottom of the bilge.
I know that as club boats we tend to go offshore in at least pairs to ensure safety of crew and craft. But of course, for commercials this is not an option (except pair trawlers ).
For the cost of an EPIRB, I am suprised that more craft who head out solo dont have them. I woudl be interested in the take up rate for EPIRBS, but they sound excellent value for money.
I have been considering a personal one for when I go solo, for