Otkud ti ta hladna voda? Dobro će nam doći na obali.

Otkud means from where? / how come? / where did ... come from? In this sentence, it is asking about the source of the water.

It is very close to odakle, and in many situations they can both be translated as where from.

A useful difference to notice:

• odakle is the more neutral from where
• otkud often sounds a bit more lively, conversational, or slightly expressive, like where did that come from?

So Otkud ti ta hladna voda? feels natural and idiomatic in speech.

Here ti is the dative singular of ti = you.

In this sentence, it does not mean the subject you in the English sense. Instead, it marks the person connected with the thing being talked about:

• Otkud ti ta hladna voda?
• literally: From where to-you that cold water?
• natural English: Where did you get that cold water?

This is a very common Croatian pattern. The dative can show the person who has, gets, experiences, or is associated with something.

Compare:

• Odakle ti auto? = Where did you get the car?
• Otkud ti to? = Where did you get that? / How do you know that?

So ti is not random; it is a normal way to say that the water is somehow with you / in your possession / obtained by you.

Croatian often leaves out words that are easily understood from context. In this sentence, the verb is simply not needed.

The full idea is something like:

• Otkud ti ta hladna voda?
• implied: Otkud ti je / došla / odakle si uzeo tu hladnu vodu?

But Croatian very naturally shortens this to the compact version. English usually needs a full verb, such as:

• Where did you get that cold water?
• Where is that cold water from?

So this is an example of elliptical speech: the grammar is shortened, but the meaning is perfectly clear to native speakers.

Ta hladna voda is in the nominative singular:

• ta = that (feminine nominative singular)
• hladna = cold (feminine nominative singular)
• voda = water (feminine nominative singular)

They all agree with each other because they describe the same noun.

Why nominative? Because in this kind of shortened question with otkud, the thing being asked about often appears in the nominative:

• Otkud ti taj kaput?
• Otkud vam toliko novca?
• Otkud ona ovdje?

So even though English might make learners expect some other structure, Croatian commonly uses the noun phrase in nominative here.

Ta means that, while ova means this.

So:

• ova hladna voda = this cold water
• ta hladna voda = that cold water

In real speech, ta often refers to something visible, already noticed, or already relevant in the conversation. It can sound like:

• that water there
• that cold water you have
• that particular cold water

So the speaker is probably pointing to or referring to a specific water that has already caught their attention.

The key expression is dobro doći, which is a common idiom meaning:

• to be useful
• to come in handy
• to be of help

So:

• Dobro će nam doći
  literally: It will come well to us
• natural English: It will come in handy for us / It’ll be useful to us

This is one of those phrases that should be learned as a chunk:

• To će mi dobro doći. = That will come in handy.
• Novac će nam dobro doći. = The money will be useful to us.

So although doći usually means to come, here the whole phrase has a more idiomatic meaning.

Nam is the dative plural of mi = we/us.

In Dobro će nam doći, it marks the people who will benefit from the water:

• nam = to us / for us

This fits the idiom dobro doći, which often takes a dative person:

• To će mi dobro doći. = That will come in handy for me.
• To će ti dobro doći. = That will be useful to you.
• To će nam dobro doći. = That will be useful to us.

So nam is there because the sentence is saying the water will be useful to us.

This is the simple future tense in Croatian.

It is made with:

• a present form of htjeti used as a clitic: ću, ćeš, će, ćemo, ćete, će
• plus the infinitive

Here:

• će = will
• doći = to come

So:

• će doći = will come

In this sentence:

• Dobro će nam doći = It will come in handy for us

A few examples:

• Doći će sutra. = He/She will come tomorrow.
• To će pomoći. = That will help.
• Voda će nam dobro doći. = The water will come in handy for us.

Croatian clitics such as će and nam usually cannot stand in the very first position of a sentence. They tend to come in the second position.

That is why Croatian often puts some stressed word first, and then the clitics follow.

Here:

• Dobro = first stressed word
• će nam = clitic cluster
• doći = infinitive

So:

• Dobro će nam doći is natural
• Će nam dobro doći is not standard word order

You could also say:

• Ta voda će nam dobro doći.

There, Ta voda comes first, and then the clitic će appears after it.

Na obali means on the shore / at the shore / on the coast / by the bank, depending on context.

Breakdown:

• na = on / at
• obali = locative singular of obala = shore, coast, bank

Because na here expresses location, it takes the locative:

• obala → na obali

The exact English translation depends on the setting:

• seaside: on the coast / at the beach / by the shore
• river or lake: on the bank / by the shore

So the sentence suggests the cold water will be useful when they are by the water or on the shore.

It can mean either, depending on context.

• hladan / hladna / hladno usually means cold
• but in everyday English, if the water is pleasantly not warm, you might translate it as cool

So Croatian does not force the same distinction English sometimes does. The context tells you whether the water is refreshingly cool or actually cold.

Here, since the next sentence says it will be useful na obali, the idea is probably that the water is pleasantly refreshing.