Very good points mjb.
But I think the underlying issue is that the current helicopter floatation system is woefully inadequate.
In this instance the floats deployed but the ship sank. In NYC the floats deployed but the ship rolled over inverted.
I feel a completely new approach to developing emergency floatation devices for helicopters landing on water is needed, where the ship won't sink or roll over no matter how bad the last stages of autorotation onto the surface turns out.