My English brain really wants to translate this as "Van a vízen egy hajó?" ... is adding the "egy" correct, or unnecessary, or completely wrong?
It's correct. If you add it, you literally ask if there's a/one ship there. "Van a vízen hajó?" is more like "Are there any ships on the water?"
Kösz.
can we say a vizen van hajó?
Or Van a hajó vizen?
Or "A vízen egy hajó van?"?
I'd like to know the same...
"Vizen van a hajó?" would be incorrect?
That is a different sentence.
Where is the ship? Is it on the water? -- Vízen van a hajó? (this sentence talks about the ship, a specific ship)
Is there a ship? Van a vízen hajó? / Van hajó a vízen? (this is not about a specific ship.)