I understand that! But, it is easier to rig underway than as the boat is below the surface...
I looked at it as just another tool in the kit. We all carry so much stuff in the name of safety! I thought this was lower in cost than a lot of the other items. It took up little space and just worked.
It is just a stop-gap item.
Like I said, we finally decided to not install one on our boat, but still think it could be of help.
Greg