Right, they would have had the time to remove the tethers if it hadn't sank. Like everything else, I'm sure that they require some amount of maintenance and I wonder if that's the sort of thing which can be tested without destroying it. I trust that my car's airbag will deploy if it's in an accident, but I really can't check that. A non-trivial number of airbags fail to deploy when they, in fact, should.

I'm not surprised that the tether is the focus, though -- it's the reason why the helicopter crashed to begin with and also prevented the passengers from escaping.