Having an Open Water Diving License, and graduated from the U.S. Military's Dive School, the first thing that is inaccurate is how long each Self Contained Underwater Breathing Apparatus (S.C.U.B.A.) tank lasted.
Divers that dived a lot like supposedly Kasey has do not hold the regulator with their hand. Holding your regulator with your hand is somethings a signal that there is something wrong with your regulator, instead of waving, pointing to your regulator and giving the go up (surface) signal. On regulators there is also a purge button to clear your regulator, that can be "accidentally" depressed if you continually hold the regulator with your hand(s). Normally before you even get into the water, you push the purge button to blow water out of the regulator mouthpiece, then insert the mouthpiece and go underwater.
Having been trained as a U.S. Military Biological Warfare Officer, we would have used a Closed Circuit Rebreathers not S.C.U.B.A. or Air Packs (S.C.B.A.), a Rebreather lasts much longer than S.C.U.B.A. or S.C.B.A. and is much lighter in weight. Weight matters as physically exhausting, like when Firefighters weight a complete Air Pack (S.C.B.A.).
High amounts of bacteria in the air would subject any exposed skin to the same levels as the air, except thru the eyes and skin and would also deplete these and body of oxygen.
Our skin is the largest organ of the human body, in Movies like Goldfinger, when a woman is painted completely with gold paint she dies from oxygen deprivation, this used to happen before with Stage Actors, in order to survive Kasey would have had to have been breathing almost 100% oxygen to compensate and risk oxygen toxicity (poisoning, hyperoxia). Oxygen would also increase the rates of bacteriological growth and contamination if these same bacteria were absorbing that amount of oxygen out of the air in the movie.
A Medical Resuscitator mask with squeeze bulb like shown in this movie does not contain oxygen, that teen that hijacked Kasey's Electric Mini Cooper would not have survived long enough to have hijacked Kasey's Electric Mini Cooper. Medical Resuscitators that do use oxygen must be connected to the Medical Facility's oxygen supply or to an oxygen cylinder ("tank").
Review by dncorp
from the Internet Movie Database.