As the European Space Agency explains, modelling is used to pick the point at which a craft will hit the upper atmosphere, and doing that at a calculated and steep angle ensures debris will fall within a certain zone.
In 2001, the Russian space station Mir reached the end of its useful life. A cargo ship docked to the craft fired its engines to take Mir out of orbit and back to Earth. Parts burned up on re-entry, while up to 25 tonnes survived, and plummeted to its watery grave at Point Nemo.
Since then, Mir has been joined by defunct satellites, rocket parts and even an automated transfer vehicle that delivered cargo to the International Space Station – an ATV called the Jules Verne.
The spacecraft that have survived space, and the fiery descent into Earth’s atmosphere, are hardy enough to resist the crushing pressure 4km (one league) down.
After re-entry there will be the occasional hole in the hull of a satellite or space station. Meaning that the pressure will quickly equalise and therefore not actually be pressure. If this didn’t happen then they’d likely bob around, wouldn’t they, rather than sinking to 4 km down?