A closer look
If you have ever awkwardly squeezed yourself through the claustrophobic hatch of a submarine and cursed the naval architects, you should probably be thanking them instead. The smaller the hole in the hull, the easier it is to maintain the intense structural integrity required to survive deep beneath the ocean. A standard-sized door would present a massive weak point against the crushing weight of the sea, resulting in an immediate and violent implosion. So go ahead and bump your head—it is better than drowning.
