Air Regeneration Stations
The plant that lets seaQuest stay under indefinitely: pulling breathable oxygen from seawater and scrubbing the crew's exhaled CO₂ back out of the air.
Details
seaQuest's endurance is limited by food and by crew patience, not by air. The boat carries regeneration plant that manufactures oxygen and strips carbon dioxide continuously, which is what makes the show's premise possible: a vessel that lives down there rather than visiting.
The series treats these as places. They are compartments with hatches, panels and readouts that characters walk into and work on, which gives a failure somewhere to happen and someone somewhere to fix it.
Real-Life
Electrolytic oxygen generators. Nuclear submarines have made their own oxygen since the first generation: pass current through water, keep the oxygen, vent the hydrogen overboard. US crews nicknamed the unit "the bomb," on the reasonable grounds that a high-pressure electrolyser full of hydrogen deserves respect. Reactor power is what makes it practical, and it is why a modern submarine's patrol length is set by food and crew endurance rather than air: exactly the constraint the show describes.
Amine CO₂ scrubbers. Cabin air is passed through a solution, historically monoethanolamine, that absorbs carbon dioxide, and is then heated to release it overboard. Alongside it sit CO/H₂ burners for trace contaminants: in a sealed hull, the slow accumulation of everything from cooking fumes to off-gassing paint is as much a problem as the CO₂ itself.
Oxygen candles. Chlorate candles produce oxygen through chemical decomposition with no power input at all, which makes them the backup of choice on submarines and spacecraft alike.
The ISS. The station runs the Russian Elektron and the American Oxygen Generation Assembly, both electrolysers, and adds something submarines have no reason to bother with: the Sabatier reactor, which combines exhaled CO₂ with waste hydrogen to recover water. Closing that loop matters in orbit, where water is the expensive thing to resupply.
Biological regeneration. ESA's MELiSSA programme has spent decades on closed-loop life support built around algae, Arthrospira, better known as spirulina, regenerating air and producing food in the same system. It remains a research programme, and it is the closest analogue to what a permanently crewed undersea vessel would actually want: a life support system that is also a farm.
