This is how US subs make oxygen from seawater
Nuclear-powered submarines are considered one of the most lethal weapons in the American arsenal and have been protecting it citizens for decades from deep down in the dark oceans. You can't see them, but they are out there defending the United States and hunting the enemy.
In modern times, many subs have the ability to dive over 170 meters, stay below the water line for up to six months without resurfacing, and can operate for 20-years before having to refuel.
The Ohio Class is the largest submarine in the US fleet and must deliver enough oxygen to the men aboard the well-designed vessel for months while remaining cloaked for days or weeks in the ocean's depths.
On average, each crew member needs 12 cubic meters of oxygen every single day to function — or more, depending on their level physical activity.
Typical vessels would have to come up for air every seven days, but with the innovative scientific method of extracting oxygen from the seawater that surrounds them, today's subs can stay under much longer.
Modern submarines now use a process known as electrolysis to separate water molecules into oxygen and hydrogen, thus creating the components for breathable air.
Once the process occurs, the oxygen is collected and continuously pumped throughout the sub's ventilation system and into the various inhabited chambers.
Check out the National Geographic video below to witness the magic of how the art of science helps submariners breath precious oxygen extracted from seawater.