"The man walks down from the water and flies up."
Translation:A férfi lesétál a vízről és felszáll.
Is there any reason why felrepül isn't accepted? Furthermore, what does the verb száll actually mean?
The verb szállni is equal to the English verb fly. The birds fly up in the sky. - A madarak felrepülnek/szállnak az égre. But if you want to say that the plane takes off - you should rather say: a repülőgép felszáll.
A víztől? No, this man is very special and actually walked on the water surface from which he stepped to the shore then. Víztől would imply that he was already off the water and walked away from there.