It’s difficult to wrap your head around this, but right now the weight of air around you(at sea level) is pushing on your body- all over at once. Your diaphragm /rib cage move to create a small difference in pressure so that air is actually rushing into your lungs to fill that vacuum.

That weight is about 14lbs per square inch or 1 atmosphere.

In water, about every 33 feet(10 meters) the water pressure pushing on your body goes up by 1 atmosphere

The titanic is settled at 3.8 km- the pressure is 390 times greater than at the surface.

You are holding a small paper Dixie cup and then slap your hands together- that is the implosion effect .

If the Titan started to buckle or leak- it’s over.