#2 Be underwater for an hour.
While still in it infancy, developments in liquid breathing techniques have introduced the possibility of reducing human dependance on gaseous air for oxygen and nitrogen.
During liquid breathing, an oxygen rich liquid called a perflurocarbon is breathed instead of air. A mechanical ventilator would regulate and sustain the flow of liquid through the lungs while an external pressurizer would re-oxygenate the liquid and release CO2.
This technology greatly reduces the risk of high water pressure related ailments that reduce the amount of time divers can remain underwater, and the pressurizer would only be limited by the charge of a battery instead of a finite amount of oxygen in a tank.
As modern technology reduces the size and energy requirements of this option it will become more feasible and affordable for humans to spend large amounts of time underwater.
Currently its is a rule of thumb that an average diver can spend about one hour at 60 feet underwater, so it is certainly a possibility with some training and experience
Happy Diving
-Six Impossible Things Team!
Sources:
http://www.livescience.com/3829-invention-humans-breathe-fish.html
