Economics is underpinned by scarcity vs the opposite. Just coming across several trillion tons of water would completely devalue their unit of currency. This find would have been the beginning of serious depression that would have dominoed into the complete collapse of financial quidproquo that cement their society. The Kazon Ogla would have been idiots to take the Ocampa's water, or admit that it exists, or behaved like they had a secret stash... In fact the most sensible thing they could do to preserve the status quo, and their on apparent wealth, would have been to destroy the underground Ocampan reservoirs. Which just leaves the magic replicator technology that was threaded through the Ocampan City, of which any one terminal therein was more than capable of remaking that ocean or making a fair stab at the impersonation of any other ocean even if it was the size of the entire universe given enough time and power... Or were the Kazon too slack witted to forecast their own doom? If they weren't, then that just means that Caretaker was too slack witted to forecast the Kazon's ability to intelligently side step doom and ruination of their civilization.
I'm not sure it was a currency in that sense. More a commodity, and one essentiell to basic survival. If they got their hands on large deposits of water, more than they need, they would start to value other less essentiell stuff.
All currency is is a commodity in absentia of something real which once upon a time a long time ago was simply the gold standard. How long would it take them to get their shit together? 5 weeks or 5 years? It's the length of the depression that can be categorized as "dark ages" if it gets silly enough.. Considering the malleability of the sects, it wouldn't be the destruction of Kazon et all, but a complete shift of the power structure of the sects if not the complete restructuring of the sects which would happen just a little bloodily as opportunists try to seize control. Neelix said the Ogla wanted water, and others have water and want other stuff. The delicate balance would be stuffed. So really, it's just the Kazon as we know them would have been destroyed rather than the kazon forever and always. My apologies for being so vague. The real problem is that everyone else in the sector would have to figure out how to pay for theOcampan cormaline that the Ogla were stock piling from their refinery on Ocampa and had now no longer any idea how to price, and since they had all the water they needed... didn't need to mine anymore anyways, so the rest of the sector was shit out of luck as their fleets began to run down because of the lack of a vital and "rare" (yes, DS9 I know) mineral essential to thei r spaece going societies. Besdes 90 percent of the water which the Kazon took was probably used as coolant for the drills burring into the Cormaline deposits...
But water isn't currency. Currency is a substitute for a thing of value, an symbol of exchange used in circumstances where direct barter is inconvenient or unfeasible. Water is an actual commodity, and trading water for other stuff is simple barter, not a monetary exchange. Never mind, of course, that the idea of a starfaring power lacking for water is completely nonsensical. Water is one of the most abundant substances in the universe. There are thousands of times more water in the comets and moons of the outer Solar System than there is on the entire planet Earth. Heck, the only reason there is water on Earth is because a small fraction of those comets crashed into it over billions of years. So the Kazon lacking water is as crazy as... oh... Voyager being unable to find deuterium.
There are no space dollars? There are no space dollars. Just barter. x amount of water = y amount of cormaline. Everyone wants cormaline which in this part of the galaxy is rare and useful enough to possibly be indispensable or irreplaceable, why else deal with scum like the kazon? Suddenly after the Ocampan oceans are opened to exploitation... 1,000,000x Water > 1,000,000/y cormaline. Until the Ogla figure out what they want, if anything, cormaline is the most priceless substance there is in that corner of the Delta Quadrant if their many, many buyers can't find a alternate supplier, who will also be jacking up their prices since the Kazon seem to be on holiday. Do the Kazon have tractor beams? Harvesting comets would difficult with grappler harpoons like Archer's Enterprise tried to waddle on with. And if they tried to build a big honking space gun on Ocampa like the human had on Mars in the 22nd century to divert the trajectory of comets towards towards the Martian polar caps, even a senile old half asleep codger like caretaker would blow it the frakk up since his big honking space guns are bigger.