I heard an interview this afternoon on NPR with David Pogue (the bbc guy who filmed a ride). He said there are 7 different ways of surfacing, including several

I heard an interview this afternoon on NPR with David Pogue (the bbc guy who filmed a ride). He said there are 7 different ways of surfacing, including several that do not require electricity and don't even require consciousness. For example, some of the ballast is attached by mounts that dissolve after a certain number of hours in water (presumably less than 96).