so to charge it on land you need some other source of energy. if you're just trying to use the steam as a weird kind of battery, then you'd have to look at energy density of steam, and also consider how well you could insulate the thing. you're probably not gonna get across an ocean with stored steam energy.

for the generators on board, again, how are they generating the electricity? it doesn't come from nowhere

(i'm just gonna ignore the fact that it makes way more sense to use the electrical power you have stored to directly drive an electric motor that drives the propeller)

same issue, where's the electric energy come from? a battery? cool, how did you charge it?

Steam isn't an energy source. You need an energy source to boil the water to make the steam. That could be coal, or gas, or oil, or wood, or something else you can burn. Or you can use nuclear energy to create the heat. either way you cant just have water, then convert it to steam magically, then power the ship.