Living a rather long life in one of the places where taxation is an art I do know a lot about taxes
but sure have missed ( so far) the universal energy tax!
I might be in a total missunderstanding here but separating salt
from water does not need any specific energy input that has to be used like the one when separating water into H2 and O2.
The salt is in solution in the water and I belive the most obvious proof for this not having anything to do with adding or subtracting energy is that the act of pouring salt into potable water does nothing in terms of energy levels...
Next thing I do have to object to is that lowering pressure increases the energy needed to boil water. The energy to increase the temperture 1 degree celsius of a given amount of water is the same no matter of the pressure, The energy to get the Water to transform into vapour is also the same irrespective of pressure.
The difference is that you do not have to add as much energy before the boiling takes place at a lower temperature and you do not transfer that much energy to for instance the bilge
when the water condensates back to water.
The point is doing the process at much lower temperatures.
The procedure of getting a low pressure situation of course costs energy but the total energy amount will be lower.
Think the opposit , pressure cooking
boils your potatoes faster and cheaper. Why?
Due higher boiling temperature at higher pressure!
I have to confess that when beeing a young hotshot fighter pilot I tried to push the envelope an climbed way higher than the max allowed service
I got a seriouse reprimand due the fact I did not wear a pressure suit and if my small positive cabin
pressure had failed I might have had problems due bubbles forming in the blood. The same thing as you have a problem with when diving and ascending too fast.
The " diving bell " analogy I can see but I do not think it has to be a diving bell sort of device nor am I convinced that you have to go that deep.