Whooooooo lives in a pineapple under the sea?
No one. Pineapples aren't suited for submerged growth. They simply can not survive underwater. Neither can humans without some form of breathing apparatus.
To allow humans to spend an extended amount of time submerged, we need to bring our oxygen with us. Typically this is done with SCUBA gear.
Fully contained submersible vehicles can also be used. They contain an atmosphere that mimics the surface.
Why do humans do this? Because without oxygen, we'd drown. Actually, we'd suffocate. Drowning is what we call oxygen deprivation caused by liquid, usually water, filling our lungs.
But, if you were submerged in an oxygen rich liquid that has the right properties, absorption of oxygen could continue.
Yes, just like in the movie, The Abyss. In fact, doctors use the technique right now to treat certain conditions caused by burns to the inside of the lungs.
These magical liquids are called perfluorocarbons. The one that is garnering the most attention right now is Perfluorohexane. It's a derivitive of hexane where all the hydrogen atoms have been replaced by flourine atoms.
Perfluorocarbons are, as the name tells you, fluorocarbons. The same nasties that, when some chlorine is attached become, chlorofluorocarbon. You know, CFC's. Ozone killers.
Anyway, fluorocarbons absorb oxygen very efficiently. And, since perfluorohexane is a liquid at room temperature, it is a very oxygen rich liquid. And, due to it's molecular make up, it's twice as efficient at transferring oxygen as normal breathing is.
So, why don't we use it more often? While it's highly efficient, our lungs are designed to transport gasses, not liquids. Our lungs don't have the structure to withstand the respiration of liquids for an extended period. Doing so would, in effect, tear the air sacs in your lungs.
Doctors, however, being the smarty pants that they are, have found perfluorohexane has a low boiling point. Just over 56 degrees centigrade. By vaporizing the liquid, doctors can fill a burn victims lungs to help healing with reduced risks of an edema occurring.
Tests have shown that animals submerged in perfluorohexane can survive fine, absorbing their oxygen from the liquid, and when removed, and reverted to normal respiration, they suffer no lasting ill effects.
So, what was science fiction just a few years ago, is actually fact. Does it come in bubble gum flavor?