Learn Croatian: Možeš li dobro plivati?

Možeš is the 'you' (singular) form of the verb moći (can/to be able to). In Croatian, verbs change their endings to match the person, so možeš already means 'you can'.

What is the purpose of the tiny word li?

li is a special question word used to make yes/no questions. When you put a verb like možeš at the start of a sentence and add li right after it, it turns a statement like 'you can' into the question 'can you?'.

Why is plivati (to swim) in its full dictionary form?

Just like in English, when you use a helper verb like 'can' (moći), the main action verb stays in its base form, which is called the infinitive. Since možeš already tells us who is doing the action, plivati does not need to change.

Why is dobro (well) placed before plivati? In English we say 'swim well'.

In Croatian, describing words (adverbs) like dobro often come right before the verb they describe. Here, it naturally sits between the question part (možeš li) and the main action (plivati).