Recently I spoke with John Clarke, on our conversation he mentioned that the NAVY is working on a CCR that could be used with umbilical as a backup; so if you still pondering about it, below are public-videos explaining the concept
MK29 rebreather

Recently I spoke with John Clarke, on our conversation he mentioned that the NAVY is working on a CCR that could be used with umbilical as a backup; so if you still pondering about it, below are public-videos explaining the concept