I'm quite sure it is acceptable to say "Nunca andei de barco..." rather than "... em um barco... the former means I have never been on one/a boat or any boat ever, whereas the latter, the acceptable answer, emphasizes 'one/a'. Anyone disagree?
for me both work equally, but surely "andei" is the most common way one would say that! (by the way, we hardly ever use "em um" but "num"
Thanks Paulenrique, exactly the clarification I was looking for. I put "num" and was surprised to find "em um" was also accepted as correct.
Is barco used for both ships and boats? Are there any other words used to distinguish between them?
For ships we frequently use navios.
What about "Eu nunca era em um barco, mas eu era em um avião"?