It's been said that the pressure at that depth is 340 times atmospheric pressure at sea level (14.7 lbs/sq inch). Hence, that's 14.7 x 340 = 4,998 psi. I'm not a physicist, but I recall from my far off schooldays that a sphere can withstand far more pressure than a cube or a cylinder. The science teacher explained that was why, in the 1930s, the 'Bathesphere' was designed as such.
Its purpose was to enable marine biologists to observe deep-sea creatures in their native environment. The dives set several consecutive world records for the deepest dive ever performed by a human. The record set by the deepest of these, to a depth of 3,028 ft (923 m) on August 15, 1934. The initial design was to be cylindrical, but it was realised that a cylinder would not withstand the pressure, so a sphere was decided upon.
Bathysphere - Wikipedia
When I saw pictures of the the ill-fated craft before news that it had imploded, I thought then, why a cylinder - not a sphere, to descend to ten times the depth of the Bathysphere? Pretty obvious really - you can house more people in a tube than a sphere and a tube is easier to construct, so commercial considerations ranked higher than physics. I dare say there will be talk about attempts to recover the bodies. It only takes a moment to realise what happens to a human body subjected to 5,000 PSI.
Apart from which, I think this picture says it all: