Who believes the (fake) existence of a water engine and why?

Question

People think that exist engines that can run with water instead of traditional fuels (gas,petroleum...).

If so,why they don't commercialise it

Answer 1

I haven't really looked into what you mean, but remember as a kid having a rocket that contained  half water and half pressurized air.   It shot up around 50 feet after a bit of pumping.   The same thing would work in a car I guess, but would only go a couple miles on a fifty gallon tank of water.

Answer 2

I am 77 and have heard it all my life. It is a scam and has no value. If it were real people would be waiting for miles to by one.