I'm kind of surprised that the OceanGate Titan submarine imploded.

I'm not a submarine engineer, but I would have expected that some of the more complex systems would have failed before the pressure vessel. Then again, it seems like they chose a seemingly cost effective design that was apparently susceptible to fatigue. Combine that with a profit motive to dive as many times as possible before retiring the hull and I suppose an implosion was practically inevitable. Oh well.