"This airplane does not take off the ground, but the water."
Translation:Ez a repülőgép nem földről száll fel, hanem vízről.
I read the Hungarian sentence as a general statement about the plane: it's designed to take off from water, not from the ground. We're not talking about it taking off from a specific body of water ("the" water) right now. To me, though, it doesn't sound quite so good in English to say "takes off from water" for some reason, and I don't think I'd ever say "takes off from ground."
If the Hungarian sentence had the definite articles in it - a földről and a vízről - then it could be read either way, and some context would be needed to understand it for sure.