Learn Hardcore Croatian: Zimi ne plivam u moru, ali bih plivala da je voda toplija. - In winter I do not swim in the sea, but I would swim if the water were warmer.

In Croatian, many time expressions are used on their own, without a preposition, in the locative form used adverbially. Zimi literally comes from zima (winter) + locative ending, but it functions like an adverb meaning “in (the) winter”.

Common pairs are:

zimi – in (the) winter
ljeti – in (the) summer
u proljeće – in (the) spring (this one does take u)

Using u zimi is not natural here; native speakers simply say zimi.

Why is the negation ne placed directly before plivam?

In Croatian, the basic way to negate a verb in the present (and most other tenses) is:

ne + finite verb

So:

plivam – I swim
ne plivam – I do not swim

You can’t put ne elsewhere (like after the verb) in standard Croatian. It always stands immediately in front of the verb it negates.

What is the difference between plivam and plivala in this sentence?

They are different verb forms:

plivam – 1st person singular, present tense, imperfective: “I swim / I am swimming.”
plivala – past participle (l‑participle), feminine singular, used here with bih to form a conditional: “I would swim.”

So:

ne plivam = I don’t (habitually) swim
bih plivala = I would swim (if some condition were true)

Why is it bih plivala and not just plivala bih or something else?

The conditional in Croatian is formed with:

the auxiliary bih / bi / bismo / biste / bi (conditional of biti, “to be”)
plus the past participle (plivao / plivala / plivali, etc.)

For I would swim (female speaker):

ja bih plivala

Because bih is a clitic, it tends to go in “second position” in the clause, so both are possible in practice:

Ali bih plivala... – very natural, clitic right after ali
Ali plivala bih... – possible, but marked/unusual in everyday speech

The everyday, neutral choice is Ali bih plivala...

What does the form bih specifically mean?

Bih is the 1st person singular conditional of biti (to be). In practice, it doesn’t mean “be” by itself here; it’s just a conditional auxiliary, similar to English “would”.

(ja) bih plivala ≈ I would swim
(ti) bi plivao / plivala ≈ you would swim
(oni) bi plivali ≈ they would swim

Why is it plivala and not plivao? What does that tell us?

The past participle in Croatian agrees with the subject’s gender and number.

plivao – masculine singular
plivala – feminine singular
plivali – masculine or mixed plural
plivale – feminine plural

So bih plivala tells us the speaker is female. A male speaker would say:

Zimi ne plivam u moru, ali bih plivao da je voda toplija.

Why is it u moru and not u more?

This is a case difference:

more – accusative (also nominative)
moru – locative (and dative)

After u, we use:

accusative for movement into something: u more = into the sea
locative for being in something: u moru = in the sea

Here the meaning is “I don’t swim in the sea”, i.e. location, not movement into it, so the locative u moru is correct.

Is there a difference between u moru and na moru?

Yes:

u moru – literally in the sea, in the water
na moru – more like at the seaside / by the sea (on the coast)

In this sentence we are clearly talking about actually swimming in the water, so u moru is used.

Example contrast:

Ljeti sam na moru. – In summer I’m at the seaside.
Ljeti plivam u moru. – In summer I swim in the sea.

How does da je voda toplija mean “if the water were warmer”?

Croatian often uses da + present tense to express unreal or hypothetical conditions, where English would use “if … were” or “if … would be”.

da je voda toplija literally: “that the water is warmer”,
but functionally: “if the water were warmer” (unreal condition).

Other possible (and more explicitly conditional) versions are:

kad bi voda bila toplija – if the water were warmer
ako bi voda bila toplija – if the water were warmer

In everyday speech, da je voda toplija is short, natural, and clearly hypothetical in this context with bih plivala.

Why is it je voda toplija and not bi voda bila toplija?

Both patterns exist but mean slightly different things:

da je voda toplija – very common, concise pattern; context and the main clause (bih plivala) show it’s hypothetical.
da bi voda bila toplija – more explicit and heavier: literally “if the water would be warmer”; also grammatical, but sounds more formal/marked here.

Note that:

da je voda bila toplija would mean “if the water had been warmer” (past unreal condition), which is a different meaning.

Why is the adjective toplija and not toplije?

Toplija is the comparative adjective agreeing with voda:

voda – feminine, singular, nominative
topla voda – warm water
toplija voda – warmer water

In voda je toplija, toplija agrees with voda (feminine singular nominative).

Toplije can also be a comparative form, but:

as a neuter adjective (for neuter nouns like more: more je toplije – the sea is warmer), or
as an adverb: Ovdje je toplije. – It is warmer here.

Since the subject is voda (feminine), toplija is required.

Why is there a comma before ali?

In Croatian, ali (but) is a coordinating conjunction that usually introduces a contrast. When it connects two clauses, a comma is normally placed before it:

Zimi ne plivam u moru, ali bih plivala da je voda toplija.

This is similar to English punctuation with “but” between two full clauses:

“I don’t swim in the sea in winter, but I would if the water were warmer.”

How does Croatian express “in winter” vs “in the winter” when there are no articles?

Croatian has no articles, so zimi can correspond to both English “in winter” and “in the winter” depending on context. The language doesn’t make that distinction grammatically.

So:

Zimi ne plivam u moru. can be understood as either
- “I don’t swim in winter.” or
- “I don’t swim in the winter.”

The choice between “winter” and “the winter” is made only when translating into English.