It might help to think about the reliability built in:
Anything which could case a catastrophic event has to be reliable for 10^-9 flying hours - that's one failure in a thousand million flying hours.
Which translates into meaning that everything crucial has a backup, often several backups. Fuselage's are built with a reserve strength factor, pressurization systems are doubled up, separate oxy systems for crew and pax.
As for surviving a ditching, it's very unlikely the aircraft with survive in any meaningful way, allowing you to make a nice egress into a life raft with a tin of spam and a whistle for attracting attention...