So umm... you see those other fuels, you know like kerolox, hydralox, and methalox, and other fuels.
You know, those are like really umm... dangerous, you could possibly die from umm... inhaling them, they may also explode, vaporizing you. They also like really expensive, you have to mish mash multiple chemicals to get your fuel. And they are like umm... like a umm... $1000000 dollars per 5 gallons I umm... think.
So instead, just umm... use water! its like really safe, and you not pollute enviroment. Its also healthy to drink and umm... its like available in lakes and ponds.
You would be amazed with the real price of fuels, it isn't that expensive and water engines (not ntr but pressure fed) are ridiculously bad