Do you know how massive offshore oil rigs float and extract oil from beneath the seabed?
Offshore Oil rigs or platforms are structures constructed for oil drilling and extraction. An oil rig is buoyant and can float like a ship.
The oil rigs have large mono-hulls and are fully equipped with processing facilities. Incredibly, oil rigs can stay afloat in one place for a prolonged time. Some oil rigs are fully functional, but some can store extracted oil and gas.
In deep waters, up to 1700 feet,...
https://www.marineinsight.com/videos/watch-how-do-offshore-oil-platforms-function/