Water seems to just be the right tool for the job in many applications. It always seemed funny to me that we have not found a better option to generate electricity over the years. Most large scale generators, no matter how complex, is just using something to heat up water and spin a really big fan in order to spin a really big magnet.
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At the end of the day, the generator stage is very efficient at turning rotary motion into electricity (98%+) and turbines are pretty efficient at extracting energy from a hot fluid and turning it into rotary motion, their efficiency is limited by physics not our design. The reason we use it is because it is legitimately the best way to extract energy from a hot fuel
The fact that its water is largely irrelevant to the actual generation of the power
All you need is a working fluid that you can heat up and ram through a turbine which cools it down and extracts the energy from it. The efficiency is defined by the ratio between the temperature of the hot side and the temperature of the cold side but since you can’t cool it below outside your cold side is almost always 300 K and up so you’ll lose efficiency there regardless of the material. The best way to boost the efficiency of your turbine is to heat up the hotside more(because you can’t cool the cold side) so many modern plants run their steam at 550-600C
Water is nice in that it sticks together at 2000C so you can heat it wayyyy up and you don’t just end up with hydrogen and oxygen. Its also non-corrosive which makes everything a lot nicer to work with. Molten salt has been used some places but you have to select your materials carefully because most salts have two halves that are each corrosive and if you heat them up they’ll try to eat through whatever you have them in.
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