Hmm. He would at first let them talk about what they find strange, knowing that for them strange might be different from what people consider so, but for more specific questions that he's likely to ask, with phrasing that takes into account, well, small animal attention span,

1. Do undead often, or recently, visit the ship?

2. Has something happened recently that they don't remember happening before?

3. Have the sailors suddenly changed how they act, or are they behaving as they ever have?

He doesn't expect anything necessarily, but probably safer to ask than not.