Learn Croatian: Vidiš li ijedan bunar s vodom? - Do you see a single well with water?

While neki means "some" or "any" in a general sense, ijedan adds strong emphasis, meaning "even a single one" or "any at all". It is especially common in questions, if-clauses, and negative contexts where you are doubting whether something exists.

ijedan bunar is the direct object, so why does it look like it is in the nominative case?

As the direct object of vidiš, it is actually in the accusative case. However, bunar (well) is a masculine inanimate noun. For masculine inanimate nouns, the accusative case is identical to the nominative case, and the adjective ijedan takes this exact form.

Why do we need the preposition s in s vodom? Doesn't the instrumental case already translate to "with"?

The bare instrumental case usually indicates the tool or means used to do something (e.g., writing with a pen). When you want to express accompaniment or contents, as in a well containing water, you must use the preposition s (or sa) before the noun.

Can the question particle li be placed later in the sentence?

No, the particle li is an enclitic, meaning it has strict placement rules. In yes/no questions, it must come immediately after the verb that begins the sentence (vidiš).