Okay, the user wants me to translate "passenger vessel" into Traditional Chinese. Let me check the rules again. The first rule says to translate all content into Traditional Chinese. The second rule states that if the content is already in Traditional Chinese, I should output it unchanged. The third rule is to provide only the translation result without any explanations.
So, the input here is "passenger vessel." I need to confirm if this is in Traditional Chinese. The term "passenger vessel" in English would be translated as "客輪" in Traditional Chinese. Since the original content is in English, I need to translate it. There's no indication that the user provided a Traditional Chinese term already, so I should translate it. The answer should just be "客輪" without any extra text. Let me make sure there are no other rules or exceptions here. The user also mentioned that for each message, I should respond with just the translation. Alright, that's straightforward. The translation is "客輪."